POKI_PUT_TOC_HERE
Command overview
Whereas the Unix toolkit is made of the separate executables cat, tail, cut,
sort, etc., Miller has subcommands, invoked as follows:
POKI_INCLUDE_ESCAPED(subcommand-example.txt)HERE
These falls into categories as follows:
Commands |
Description |
cat,
cut,
head,
sort,
tac,
tail,
top,
uniq
|
Analogs of their Unix-toolkit namesakes, discussed below as well as in
POKI_PUT_LINK_FOR_PAGE(feature-comparison.html)HERE |
filter,
put,
step
|
awk-like functionality |
histogram,
stats1,
stats2
|
Statistically oriented |
group-by,
group-like,
having-fields
|
Particularly oriented toward POKI_PUT_LINK_FOR_PAGE(record-heterogeneity.html)HERE, although
all Miller commands can handle heterogeneous records
|
count-distinct,
label,
rename,
rename,
reorder
|
These draw from other sources (see also POKI_PUT_LINK_FOR_PAGE(originality.html)HERE):
count-distinct is SQL-ish, and
rename can be done by sed (which does it faster:
see POKI_PUT_LINK_FOR_PAGE(performance.html)HERE).
|
On-line help
Examples:
POKI_RUN_COMMAND{{mlr --help}}HERE
POKI_RUN_COMMAND{{mlr sort --help}}HERE
Data types
Miller’s input and output are all string-oriented: there is (as of
August 2015 anyway) no support for binary record packing. In this sense,
everything is a string in and out of Miller. During processing, field names
are always strings, even if they have names like "3"; field values are usually
strings. Field values’ ability to be interpreted as a non-string type
only has meaning when comparison or function operations are done on them. And
it is an error condition if Miller encounters non-numeric (or otherwise
mistyped) data in a field in which it has been asked to do numeric (or
otherwise type-specific) operations.
Field values are treated as numeric for the following:
Numeric sort: mlr sort -n, mlr sort -nr.
Statistics: mlr histogram, mlr stats1, mlr stats2.
Cross-record arithmetic: mlr step.
For mlr put and mlr filter:
Miller’s types for function processing are null (empty
string), error, string, float (double-precision),
int (64-bit signed), and boolean.
On input, string values representable as numbers, e.g. "3" or "3.1", are
treated as int or float, respectively. If a record has x=1,y=2 then
mlr put '$z=$x+$y' will produce x=1,y=2,z=3, and mlr put
'$z=$x.$y' gives an error. To coerce back to string for processing, use
the string function: mlr put '$z=string($x).string($y)' will
produce x=1,y=2,z=12.
On input, string values representable as boolean (e.g. "true",
"false") are not automatically treated as boolean. (This is
because "true" and "false" are ordinary words, and auto
string-to-boolean on a column consisting of words would result in some strings
mixed with some booleans.) Use the boolean function to coerce: e.g.
giving the record x=1,y=2,w=false to mlr put '$z=($x<$y) ||
boolean($w)'.
Functions take types as described in mlr --help-all-functions:
for example, log10 takes float input and produces float output,
gmt2sec maps string to int, and sec2gmt maps int to string.
All math functions described in mlr --help-all-functions take
integer as well as float input.
Null data
One of Miller’s key features is its support for heterogeneous data.
Accordingly, if you try to sort on field hostname when not all records in the data
stream have a field named hostname, it is not an error (although you could
pre-filter the data stream using mlr having-fields --at-least hostname then sort ...).
Rather, records lacking one or more sort keys are simply output contiguously by mlr sort.
Field values may also be null by being
specified with present key but empty value: e.g. sending x=,y=2 to mlr put '$z=$x+$y'.
Rules for null-handling:
- Records with one or more null sort-field values sort after records with all sort-field values present:
POKI_RUN_COMMAND{{mlr --opprint cat data/sort-null.dat}}HERE
POKI_RUN_COMMAND{{mlr --opprint sort -n a data/sort-null.dat}}HERE
POKI_RUN_COMMAND{{mlr --opprint sort -nr a data/sort-null.dat}}HERE
- Functions which have one or more null arguments produce null output: e.g.
POKI_RUN_COMMAND{{echo 'x=2,y=3' | mlr put '$a=$x+$y'}}HERE
POKI_RUN_COMMAND{{echo 'x=,y=3' | mlr put '$a=$x+$y'}}HERE
POKI_RUN_COMMAND{{echo 'x=,y=3' | mlr put '$a=log($x);$b=log($y)'}}HERE
- The min and max functions are special: if one argument is non-null, it wins:
POKI_RUN_COMMAND{{echo 'x=,y=3' | mlr put '$a=min($x,$y);$b=max($x,$y)'}}HERE
I/O options
Formats
Options:
--dkvp --idkvp --odkvp
--nidx --inidx --onidx
--csv --icsv --ocsv
--csvlite --icsvlite --ocsvlite
--pprint --ipprint --ppprint --right
--xtab --ixtab --oxtab
These are as discussed in POKI_PUT_LINK_FOR_PAGE(file-formats.html)HERE, with the exception of --right
which makes pretty-printed output right-aligned:
POKI_RUN_COMMAND{{mlr --opprint cat data/small}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint --right cat data/small}}HERE
|
Additional notes:
Use --csv, --pprint, etc. when the input and output formats are the same.
Use --icsv --opprint, etc. when you want format conversion as part of what Miller does to your data.
DKVP (key-value-pair) format is the default for input and output. So,
--oxtab is the same as --idkvp --oxtab.
Compression
Options:
--prepipe {command}
The prepipe command is anything which reads from standard input and produces data acceptable to
Miller. Nominally this allows you to use whichever decompression utilities you have installed on your
system, on a per-file basis. If the command has flags, quote them: e.g. mlr --prepipe 'zcat -cf'. Examples:
# These two produce the same output:
$ gunzip < myfile1.csv.gz | mlr cut -f hostname,uptime
$ mlr --prepipe gunzip cut -f hostname,uptime myfile1.csv.gz
# With multiple input files you need --prepipe:
$ mlr --prepipe gunzip cut -f hostname,uptime myfile1.csv.gz myfile2.csv.gz
$ mlr --prepipe gunzip --idkvp --oxtab cut -f hostname,uptime myfile1.dat.gz myfile2.dat.gz
# Similar to the above, but with compressed output as well as input:
$ gunzip < myfile1.csv.gz | mlr cut -f hostname,uptime | gzip > outfile.csv.gz
$ mlr --prepipe gunzip cut -f hostname,uptime myfile1.csv.gz | gzip > outfile.csv.gz
$ mlr --prepipe gunzip cut -f hostname,uptime myfile1.csv.gz myfile2.csv.gz | gzip > outfile.csv.gz
# Similar to the above, but with different compression tools for input and output:
$ gunzip < myfile1.csv.gz | mlr cut -f hostname,uptime | xz -z > outfile.csv.xz
$ xz -cd < myfile1.csv.xz | mlr cut -f hostname,uptime | gzip > outfile.csv.xz
$ mlr --prepipe 'xz -cd' cut -f hostname,uptime myfile1.csv.xz myfile2.csv.xz | xz -z > outfile.csv.xz
... etc.
Record/field/pair separators
Miller has record separators IRS and ORS, field
separators IFS and OFS, and pair separators IPS and
OPS. For example, in the DKVP line a=1,b=2,c=3, the record
separator is newline, field separator is comma, and pair separator is the
equals sign. These are the default values.
Options:
--rs --irs --ors
--fs --ifs --ofs --repifs
--ps --ips --ops
You can change a separator from input to output via e.g. --ifs =
--ofs :. Or, you can specify that the same separator is to be used for
input and output via e.g. --fs :.
The pair separator is only relevant to DKVP format.
Pretty-print and xtab formats ignore the separator arguments altogether.
The --repifs means that multiple successive occurrences of the
field separator count as one. For example, in CSV data we often signify nulls
by empty strings, e.g. 2,9,,,,,6,5,4. On the other hand, if the field
separator is a space, it might be more natural to parse 2 4 5 the
same as 2 4 5: --repifs --ifs ' ' lets this happen. In fact,
the --ipprint option above is internally implemented in terms of
--repifs.
Just write out the desired separator, e.g. --ofs '|'. But you
may use the symbolic names newline, space, tab,
pipe, or semicolon if you like.
Number formatting
The command-line option --ofmt {format string} is the global
number format for commands which generate numeric output, e.g.
stats1, stats2, histogram, and step, as
well as mlr put. Examples:
POKI_CARDIFY(--ofmt %.9le --ofmt %.6lf --ofmt %.0lf)HERE
These are just C printf formats applied to double-precision
numbers. Please don’t use %s or %d. Additionally, if
you use leading width (e.g. %18.12lf) then the output will contain
embedded whitespace, which may not be what you want if you pipe the output to
something else, particularly CSV. I use Miller’s pretty-print format
(mlr --opprint) to column-align numerical data.
To apply formatting to a single field, overriding the global
ofmt, use fmtnum function within mlr put. For example:
POKI_RUN_COMMAND{{echo 'x=3.1,y=4.3' | mlr put '$z=fmtnum($x*$y,"%08lf")'}}HERE
POKI_RUN_COMMAND{{echo 'x=0xffff,y=0xff' | mlr put '$z=fmtnum(int($x*$y),"%08llx")'}}HERE
Input conversion from hexadecimal is done automatically on fields handled
by mlr put and mlr filter as long as the field value begins
with "0x". To apply output conversion to hexadecimal on a single column, you
may use fmtnum, or the keystroke-saving hexfmt function.
Example:
POKI_RUN_COMMAND{{echo 'x=0xffff,y=0xff' | mlr put '$z=hexfmt($x*$y)'}}HERE
Data transformations
bar
Cheesy bar-charting.
POKI_RUN_COMMAND{{mlr bar -h}}HERE
POKI_RUN_COMMAND{{mlr --opprint cat data/small}}HERE
POKI_RUN_COMMAND{{mlr --opprint bar --lo 0 --hi 1 -f x,y data/small}}HERE
POKI_RUN_COMMAND{{mlr --opprint bar --lo 0.4 --hi 0.6 -f x,y data/small}}HERE
POKI_RUN_COMMAND{{mlr --opprint bar --auto -f x,y data/small}}HERE
bootstrap
POKI_RUN_COMMAND{{mlr bootstrap --help}}HERE
The canonical use for bootstrap sampling is to put error bars on statistical quantities, such as mean. For example:
$ mlr --opprint stats1 -a mean,count -f u -g color data/colored-shapes.dkvp
color u_mean u_count
yellow 0.497129 1413
red 0.492560 4641
purple 0.494005 1142
green 0.504861 1109
blue 0.517717 1470
orange 0.490532 303
$ mlr --opprint bootstrap then stats1 -a mean,count -f u -g color data/colored-shapes.dkvp
color u_mean u_count
yellow 0.500651 1380
purple 0.501556 1111
green 0.503272 1068
red 0.493895 4702
blue 0.512529 1496
orange 0.521030 321
$ mlr --opprint bootstrap then stats1 -a mean,count -f u -g color data/colored-shapes.dkvp
color u_mean u_count
yellow 0.498046 1485
blue 0.513576 1417
red 0.492870 4595
orange 0.507697 307
green 0.496803 1075
purple 0.486337 1199
$ mlr --opprint bootstrap then stats1 -a mean,count -f u -g color data/colored-shapes.dkvp
color u_mean u_count
blue 0.522921 1447
red 0.490717 4617
yellow 0.496450 1419
purple 0.496523 1192
green 0.507569 1111
orange 0.468014 292
cat
Most useful for format conversions (see
POKI_PUT_LINK_FOR_PAGE(file-formats.html)HERE), and concatenating multiple
same-schema CSV files to have the same header:
POKI_RUN_COMMAND{{mlr cat -h}}HERE
POKI_RUN_COMMAND{{cat a.csv}}HERE
|
POKI_RUN_COMMAND{{cat b.csv}}HERE
|
POKI_RUN_COMMAND{{mlr --csv cat a.csv b.csv}}HERE
|
|
POKI_RUN_COMMAND{{mlr --icsv --oxtab cat a.csv b.csv}}HERE
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POKI_RUN_COMMAND{{mlr --csv cat -n a.csv b.csv}}HERE
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check
POKI_RUN_COMMAND{{mlr check --help}}HERE
decimate
POKI_RUN_COMMAND{{mlr decimate --help}}HERE
count-distinct
POKI_RUN_COMMAND{{mlr count-distinct --help}}HERE
POKI_RUN_COMMAND{{mlr count-distinct -f a,b then sort -nr count data/medium}}HERE
POKI_RUN_COMMAND{{mlr count-distinct -n -f a,b data/medium}}HERE
cut
POKI_RUN_COMMAND{{mlr cut --help}}HERE
POKI_RUN_COMMAND{{mlr --opprint cat data/small}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint cut -f y,x,i data/small}}HERE
|
POKI_RUN_COMMAND{{echo 'a=1,b=2,c=3' | mlr cut -f b,c,a}}HERE
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POKI_RUN_COMMAND{{echo 'a=1,b=2,c=3' | mlr cut -o -f b,c,a}}HERE
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filter
POKI_RUN_COMMAND{{mlr filter --help}}HERE
Field names must be specified using a $ in filter and
put expressions, even though they don’t appear in the data
stream. For integer-indexed data, this looks like awk’s
$1,$2,$3. Likewise, enclose string literals in double quotes in
filter expressions even though they don’t appear in file data.
In particular, mlr filter '$x=="abc"' passes through the record
x=abc.
The filter command supports the same built-in variables as for
put, all awk-inspired: NF,
NR, FNR, FILENUM, and FILENAME. This
selects the 2nd record from each matching file:
POKI_RUN_COMMAND{{mlr filter 'FNR == 2' data/small*}}HERE
Expressions may be arbitrarily complex:
POKI_RUN_COMMAND{{mlr --opprint filter '$a == "pan" || $b == "wye"' data/small}}HERE
POKI_RUN_COMMAND{{mlr --opprint filter '($x > 0.5 && $y > 0.5) || ($x < 0.5 && $y < 0.5)' then stats2 -a corr -f x,y data/medium}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint filter '($x > 0.5 && $y < 0.5) || ($x < 0.5 && $y > 0.5)' then stats2 -a corr -f x,y data/medium}}HERE
|
Newlines within the expression are ignored, which can help increase legibility of complex expressions:
POKI_INCLUDE_ESCAPED(filter-multiline-example.txt)HERE
grep
POKI_RUN_COMMAND{{mlr grep -h}}HERE
group-by
POKI_RUN_COMMAND{{mlr group-by --help}}HERE
This is similar to sort but with less work. Namely, Miller’s
sort has three steps: read through the data and append linked lists of records,
one for each unique combination of the key-field values; after all records
are read, sort the key-field values; then print each record-list. The group-by
operation simply omits the middle sort. An example should make this more
clear.
POKI_RUN_COMMAND{{mlr --opprint group-by a data/small}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint sort -f a data/small}}HERE
|
In this example, since the sort is on field a, the first step is
to group together all records having the same value for field a; the
second step is to sort the distinct a-field values pan,
eks, and wye into eks, pan, and
wye; the third step is to print out the record-list for
a=eks, then the record-list for a=pan, then the record-list
for a=wye. The group-by operation omits the middle sort and just puts
like records together, for those times when a sort isn’t desired. In
particular, the ordering of group-by fields for group-by is the order in which
they were encountered in the data stream, which in some cases may be more interesting
to you.
group-like
POKI_RUN_COMMAND{{mlr group-like --help}}HERE
This groups together records having the same schema (i.e. same ordered list of field names)
which is useful for making sense of time-ordered output as described in
POKI_PUT_LINK_FOR_PAGE(record-heterogeneity.html)HERE — in particular, in
preparation for CSV or pretty-print output.
POKI_RUN_COMMAND{{mlr cat data/het.dkvp}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint group-like data/het.dkvp}}HERE
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having-fields
POKI_RUN_COMMAND{{mlr having-fields --help}}HERE
Similar to group-like, this retains records with specified schema.
POKI_RUN_COMMAND{{mlr cat data/het.dkvp}}HERE
|
POKI_RUN_COMMAND{{mlr having-fields --at-least resource data/het.dkvp}}HERE
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POKI_RUN_COMMAND{{mlr having-fields --which-are resource,ok,loadsec data/het.dkvp}}HERE
|
head
POKI_RUN_COMMAND{{mlr head --help}}HERE
Note that head is distinct from top
— head shows fields which appear first in the data stream;
top shows fields which are numerically largest (or smallest).
POKI_RUN_COMMAND{{mlr --opprint head -n 4 data/medium}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint head -n 1 -g b data/medium}}HERE
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histogram
POKI_RUN_COMMAND{{mlr histogram --help}}HERE
This is just a histogram; there’s not too much to say here. A note about
binning, by example: Suppose you use --lo 0.0 --hi 1.0 --nbins 10 -f
x. The input numbers less than 0 or greater than 1 aren’t counted
in any bin. Input numbers equal to 1 are counted in the last bin. That is, bin
0 has 0.0 ≤ x < 0.1, bin 1 has 0.1 ≤ x < 0.2,
etc., but bin 9 has 0.9 ≤ x ≤ 1.0.
POKI_RUN_COMMAND{{mlr --opprint put '$x2=$x**2;$x3=$x2*$x' then histogram -f x,x2,x3 --lo 0 --hi 1 --nbins 10 data/medium}}HERE
join
POKI_RUN_COMMAND{{mlr join --help}}HERE
Examples:
Join larger table with IDs with smaller ID-to-name lookup table, showing only paired records:
POKI_RUN_COMMAND{{mlr --icsvlite --opprint cat data/join-left-example.csv}}HERE
|
POKI_RUN_COMMAND{{mlr --icsvlite --opprint cat data/join-right-example.csv}}HERE
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POKI_RUN_COMMAND{{mlr --icsvlite --opprint join -u -j id -r idcode -f data/join-left-example.csv data/join-right-example.csv}}HERE
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Same, but with sorting the input first:
POKI_RUN_COMMAND{{mlr --icsvlite --opprint sort -f idcode then join -j id -r idcode -f data/join-left-example.csv data/join-right-example.csv}}HERE
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Same, but showing only unpaired records:
POKI_RUN_COMMAND{{mlr --icsvlite --opprint join --np --ul --ur -u -j id -r idcode -f data/join-left-example.csv data/join-right-example.csv}}HERE
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Use prefixing options to disambiguate between otherwise identical non-join field names:
POKI_RUN_COMMAND{{mlr --csvlite --opprint cat data/self-join.csv data/self-join.csv}}HERE
|
POKI_RUN_COMMAND{{mlr --csvlite --opprint join -j a --lp left_ --rp right_ -f data/self-join.csv data/self-join.csv}}HERE
|
Use zero join columns:
POKI_RUN_COMMAND{{mlr --csvlite --opprint join -j "" --lp left_ --rp right_ -f data/self-join.csv data/self-join.csv}}HERE
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label
POKI_RUN_COMMAND{{mlr label --help}}HERE
See also rename.
Example: Files such as /etc/passwd, /etc/group, and so on
have implicit field names which are found in section-5 manpages. These field names may be made explicit as follows:
POKI_INCLUDE_ESCAPED(data/label-example.txt)HERE
Likewise, if you have CSV/CSV-lite input data which has somehow been bereft of its header line, you can re-add a header line using --implicit-csv-header and label:
POKI_RUN_COMMAND{{cat data/headerless.csv}}HERE
POKI_RUN_COMMAND{{mlr --csv --rs lf --implicit-csv-header cat data/headerless.csv}}HERE
POKI_RUN_COMMAND{{mlr --csv --rs lf --implicit-csv-header label name,age,status data/headerless.csv}}HERE
POKI_RUN_COMMAND{{mlr --icsv --rs lf --implicit-csv-header --opprint label name,age,status data/headerless.csv}}HERE
merge-fields
POKI_RUN_COMMAND{{mlr merge-fields --help}}HERE
This is like mlr stats1 but all accumulation is done across fields
within each given record: horizontal rather than vertical statistics, if you
will.
Examples:
POKI_RUN_COMMAND{{mlr --csvlite --opprint cat data/inout.csv}}HERE
POKI_RUN_COMMAND{{mlr --csvlite --opprint merge-fields -a min,max,sum -c _in,_out data/inout.csv}}HERE
POKI_RUN_COMMAND{{mlr --csvlite --opprint merge-fields -k -a sum -c _in,_out data/inout.csv}}HERE
put
POKI_RUN_COMMAND{{mlr put --help}}HERE
Field names must be specified using a $ in filter and put
expressions, even though they don’t appear in the data stream. For
integer-indexed data, this looks like awk’s $1,$2,$3.
Likewise, enclose string literals in double quotes in put
expressions even though they don’t appear in file data. In particular,
mlr put '$x=="abc"' creates the field x=abc.
Multiple expressions may be given, separated by semicolons, and each may refer to the ones before:
POKI_RUN_COMMAND{{ruby -e '10.times{|i|puts "i=#{i}"}' | mlr --opprint put '$j=$i+1;$k=$i+$j'}}HERE
Miller supports the following five built-in variables for filter
and put, all awk-inspired: NF, NR,
FNR, FILENUM, and FILENAME.
POKI_RUN_COMMAND{{mlr --opprint put '$nf=NF; $nr=NR; $fnr=FNR; $filenum=FILENUM; $filename=FILENAME' data/small data/small2}}HERE
Newlines within the expression are ignored, which can help increase legibility of complex expressions:
POKI_INCLUDE_ESCAPED(put-multiline-example.txt)HERE
regularize
POKI_RUN_COMMAND{{mlr regularize --help}}HERE
This exists since hash-map software in various languages and tools
encountered in the wild does not always print similar rows with fields in the
same order: mlr regularize helps clean that up.
See also reorder.
rename
POKI_RUN_COMMAND{{mlr rename --help}}HERE
POKI_RUN_COMMAND{{mlr --opprint cat data/small}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint rename i,INDEX,b,COLUMN2 data/small}}HERE
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As discussed in POKI_PUT_LINK_FOR_PAGE(performance.html)HERE, sed
is significantly faster than Miller at doing this. However, Miller is
format-aware, so it knows to do renames only within specified field keys and
not any others, nor in field values which may happen to contain the same
pattern. Example:
POKI_RUN_COMMAND{{sed 's/y/COLUMN5/g' data/small}}HERE
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POKI_RUN_COMMAND{{mlr rename y,COLUMN5 data/small}}HERE
|
See also label.
reorder
POKI_RUN_COMMAND{{mlr reorder --help}}HERE
This pivots specified field names to the start or end of the record — for
example when you have highly multi-column data and you want to bring a field or
two to the front of line where you can give a quick visual scan.
POKI_RUN_COMMAND{{mlr --opprint cat data/small}}HERE
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POKI_RUN_COMMAND{{mlr --opprint reorder -f i,b data/small}}HERE
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POKI_RUN_COMMAND{{mlr --opprint reorder -e -f i,b data/small}}HERE
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sample
POKI_RUN_COMMAND{{mlr sample --help}}HERE
This is reservoir-sampling: select k items from n with
uniform probability and no repeats in the sample. (If n is less than
k, then of course only n samples are produced.) With -g
{field names}, produce a k-sample for each distinct value of the
specified field names.
POKI_INCLUDE_ESCAPED(data/sample-example.txt)HERE
Note that no output is produced until all inputs are in. Another way to do
sampling, which works in the streaming case, is mlr filter 'urand() &
0.001' where you tune the 0.001 to meet your needs.
sec2gmt
POKI_RUN_COMMAND{{mlr sec2gmt -h}}HERE
sort
POKI_RUN_COMMAND{{mlr sort --help}}HERE
Example:
POKI_RUN_COMMAND{{mlr --opprint sort -f a -nr x data/small}}HERE
Here’s an example filtering log data: suppose multiple threads (labeled here by color) are all logging progress counts to a single log file. The log file is (by nature) chronological, so the progress of various threads is interleaved:
POKI_RUN_COMMAND{{head -n 10 data/multicountdown.dat}}HERE
We can group these by thread by sorting on the thread ID (here,
color). Since Miller’s sort is stable, this means that
timestamps within each thread’s log data are still chronological:
POKI_RUN_COMMAND{{head -n 20 data/multicountdown.dat | mlr --opprint sort -f color}}HERE
Any records not having all specified sort keys will appear at the end of the output, in the order they
were encountered, regardless of the specified sort order:
POKI_RUN_COMMAND{{mlr sort -n x data/sort-missing.dkvp}}HERE
POKI_RUN_COMMAND{{mlr sort -nr x data/sort-missing.dkvp}}HERE
stats1
POKI_RUN_COMMAND{{mlr stats1 --help}}HERE
These are simple univariate statistics on one or more number-valued fields
(count and mode apply to non-numeric fields as well),
optionally categorized by one or more other fields.
POKI_RUN_COMMAND{{mlr --oxtab stats1 -a count,sum,min,p10,p50,mean,p90,max -f x,y data/medium}}HERE
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POKI_RUN_COMMAND{{mlr --opprint stats1 -a mean -f x,y -g b then sort -f b data/medium}}HERE
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POKI_RUN_COMMAND{{mlr --opprint stats1 -a p50,p99 -f u,v -g color then put '$ur=$u_p99/$u_p50;$vr=$v_p99/$v_p50' data/colored-shapes.dkvp}}HERE
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POKI_RUN_COMMAND{{mlr --opprint count-distinct -f shape then sort -nr count data/colored-shapes.dkvp}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint stats1 -a mode -f color -g shape data/colored-shapes.dkvp}}HERE
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stats2
POKI_RUN_COMMAND{{mlr stats2 --help}}HERE
These are simple bivariate statistics on one or more pairs of number-valued
fields, optionally categorized by one or more fields.
POKI_RUN_COMMAND{{mlr --oxtab put '$x2=$x*$x; $xy=$x*$y; $y2=$y**2' then stats2 -a cov,corr -f x,y,y,y,x2,xy,x2,y2 data/medium}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint put '$x2=$x*$x; $xy=$x*$y; $y2=$y**2' then stats2 -a linreg-ols,r2 -f x,y,y,y,xy,y2 -g a data/medium}}HERE
|
Here’s an example simple line-fit. The x and y
fields of the data/medium dataset are just independent uniformly
distributed on the unit interval. Here we remove half the data and fit a line to it.
POKI_INCLUDE_ESCAPED(data/linreg-example.txt)HERE
I use pgr for
plotting; here’s a screenshot.
(Thanks Drew Kunas for a good conversation about PCA!)
Here’s an example estimating time-to-completion for a set of jobs.
Input data comes from a log file, with number of work units left to do in the
count field and accumulated seconds in the upsec field,
labeled by the color field:
POKI_RUN_COMMAND{{head -n 10 data/multicountdown.dat}}HERE
We can do a linear regression on count remaining as a function of time: with c = m*u+b we want to find the
time when the count goes to zero, i.e. u=-b/m.
POKI_RUN_COMMAND{{mlr --oxtab stats2 -a linreg-pca -f upsec,count -g color then put '$donesec = -$upsec_count_pca_b/$upsec_count_pca_m' data/multicountdown.dat}}HERE
step
POKI_RUN_COMMAND{{mlr step --help}}HERE
Most Miller commands are record-at-a-time, with the exception of stats1,
stats2, and histogram which compute aggregate output. The
step command is intermediate: it allows the option of adding fields
which are functions of fields from previous records. Rsum is short for running sum.
POKI_RUN_COMMAND{{mlr --opprint step -a delta,rsum,counter -f x data/medium | head -15}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint step -a delta,rsum,counter -f x -g a data/medium | head -15}}HERE
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POKI_RUN_COMMAND{{mlr --opprint step -a ewma -f x -d 0.1,0.9 ../doc/data/medium | head -15}}HERE
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Example deriving uptime-delta from system uptime:
POKI_INCLUDE_ESCAPED(data/ping-delta-example.txt)HERE
tac
POKI_RUN_COMMAND{{mlr tac --help}}HERE
Prints the records in the input stream in reverse order. Note: this
requires Miller to retain all input records in memory before any output records
are produced.
POKI_RUN_COMMAND{{mlr --icsv --opprint cat a.csv}}HERE
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POKI_RUN_COMMAND{{mlr --icsv --opprint cat b.csv}}HERE
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POKI_RUN_COMMAND{{mlr --icsv --opprint tac a.csv b.csv}}HERE
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POKI_RUN_COMMAND{{mlr --icsv --opprint put '$filename=FILENAME' then tac a.csv b.csv}}HERE
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tail
POKI_RUN_COMMAND{{mlr tail --help}}HERE
Prints the last n records in the input stream, optionally by category.
POKI_RUN_COMMAND{{mlr --opprint tail -n 4 data/colored-shapes.dkvp}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint tail -n 1 -g shape data/colored-shapes.dkvp}}HERE
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top
POKI_RUN_COMMAND{{mlr top --help}}HERE
Note that top is distinct from head
— head shows fields which appear first in the data stream;
top shows fields which are numerically largest (or smallest).
POKI_RUN_COMMAND{{mlr --opprint top -n 4 -f x data/medium}}HERE
|
POKI_RUN_COMMAND{{mlr --opprint top -n 2 -f x -g a then sort -f a data/medium}}HERE
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uniq
POKI_RUN_COMMAND{{mlr uniq --help}}HERE
POKI_RUN_COMMAND{{wc -l data/colored-shapes.dkvp}}HERE
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POKI_RUN_COMMAND{{mlr uniq -g color,shape data/colored-shapes.dkvp}}HERE
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POKI_RUN_COMMAND{{mlr --opprint uniq -g color,shape -c then sort -f color,shape data/colored-shapes.dkvp}}HERE
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POKI_RUN_COMMAND{{mlr --opprint uniq -n -g color,shape data/colored-shapes.dkvp}}HERE
|
then-chaining
In accord with the
Unix philosophy, you can pipe data into or out of
Miller. For example:
POKI_CARDIFY(mlr cut --complement -f os_version *.dat | mlr sort -f hostname,uptime)HERE
You can, if you like, instead simply chain commands together using the
then keyword:
POKI_CARDIFY(mlr cut --complement -f os_version then sort -f hostname,uptime *.dat)HERE
Here’s a performance comparison:
POKI_INCLUDE_ESCAPED(data/then-chaining-performance.txt)HERE
There are two reasons to use then-chaining: one is for performance, although I
don’t expect this to be a win in all cases. Using then-chaining avoids
redundant string-parsing and string-formatting at each pipeline step: instead
input records are parsed once, they are fed through each pipeline stage in
memory, and then output records are formatted once. On the other hand, Miller
is single-threaded, while modern systems are usually multi-processor, and when
streaming-data programs operate through pipes, each one can use a CPU. Rest
assured you get the same results either way.
The other reason to use then-chaining is for simplicity: you don’t
have re-type formatting flags (e.g. --csv --rs lf --fs tab) at every
pipeline stage.
Functions for filter and put
POKI_RUN_COMMAND{{mlr --help-all-functions}}HERE
Operator precedence
Operators are listed in order of decreasing precedence, highest first.
Operators Associativity
--------- -------------
() left to right
** right to left
! ~ unary+ unary- & right to left
binary* / // % left to right
binary+ binary- . left to right
<< >> left to right
& left to right
^ left to right
| left to right
< <= > >= left to right
== != =~ !=~ left to right
&& left to right
^^ left to right
|| left to right
= N/A for Miller (there is no $a=$b=$c)
Operator and function semantics
Functions are in general pass-throughs straight to the system-standard C
library.
The min and max functions are different from other
multi-argument functions which return null if any of their inputs are null: for
min and max, by contrast, if one argument is null, the other
is returned.
Symmetrically with respect to the bitwise OR, XOR, and AND operators
|, ^, &, Miller has logical operators
||, ^^, &&: the logical XOR not existing in
C.
The exponentiation operator ** is familiar from many languages.
The regex-match and regex-not-match operators =~ and
!=~ are similar to those in Ruby and Perl.
Arithmetic
Input scanning
Numbers in Miller are double-precision float or 64-bit signed integers.
Anything scannable as int, e.g 123 or 0xabcd, is treated as
an integer; otherwise, input scannable as float (4.56 or 8e9)
is treated as float; everything else is a string.
If you want all numbers to be treated as floats, then you may use
float() in your filter/put expressions (e.g. replacing $c = $a *
$b with $c = float($a) * float($b)) — or, more simply, use
mlr filter -F and mlr put -F which forces all numeric input,
whether from expression literals or field values, to float. Likewise mlr
stats1 -F and mlr step -F force integerable accumulators (such as
count) to be done in floating-point.
Conversion by math routines
For most math functions, integers are cast to float on input, and produce
float output: e.g. exp(0) = 1.0 rather than 1. The
following, however, produce integer output if their inputs are integers:
+ - * / // % abs
ceil floor max min round
roundm sgn. As well, stats1 -a min, stats1 -a
max, stats1 -a sum, step -a delta, and step -a
rsum produce integer output if their inputs are integers.
Conversion by arithmetic operators
The sum, difference, and product of integers is again integer, except for
when that would overflow a 64-bit integer at which point Miller converts the
result to float.
The short of it is that Miller does this transparently for you so you
needn’t think about it.
Implementation details of this, for the interested: integer adds and
subtracts overflow by at most one bit so it suffices to check sign-changes.
Thus, Miller allows you to add and subtract arbitrary 64-bit signed integers,
converting only to float precisely when the result is less than -263
or greater than 263-1. Multiplies, on the other hand, can overflow
by a word size and a sign-change technique does not suffice to detect overflow.
Instead Miller tests whether the floating-point product exceeds the
representable integer range. Now, 64-bit integers have 64-bit precision while
IEEE-doubles have only 52-bit mantissas — so, there are 53 bits including
implicit leading one. The following experiment explicitly demonstrates the
resolution at this range:
64-bit integer 64-bit integer Casted to double Back to 64-bit
in hex in decimal integer
0x7ffffffffffff9ff 9223372036854774271 9223372036854773760.000000 0x7ffffffffffff800
0x7ffffffffffffa00 9223372036854774272 9223372036854773760.000000 0x7ffffffffffff800
0x7ffffffffffffbff 9223372036854774783 9223372036854774784.000000 0x7ffffffffffffc00
0x7ffffffffffffc00 9223372036854774784 9223372036854774784.000000 0x7ffffffffffffc00
0x7ffffffffffffdff 9223372036854775295 9223372036854774784.000000 0x7ffffffffffffc00
0x7ffffffffffffe00 9223372036854775296 9223372036854775808.000000 0x8000000000000000
0x7ffffffffffffffe 9223372036854775806 9223372036854775808.000000 0x8000000000000000
0x7fffffffffffffff 9223372036854775807 9223372036854775808.000000 0x8000000000000000
That is, one cannot check an integer product to see if it is precisely
greater than 263-1 or less than -263 using either integer
arithmetic (it may have already overflowed) or using double-precision (due to
granularity). Instead Miller checks for overflow in 64-bit integer
multiplication by seeing whether the absolute value of the double-precision
product exceeds the largest representable IEEE double less than 263,
which we see from the listing above is 9223372036854774784. (An alternative
would be to do all integer multiplies using handcrafted multi-word 128-bit
arithmetic. This approach is not taken.)
Pythonic division
Division and remainder are
pythonic:
Quotient of integers is floating-point: 7/2 is 3.5.
Integer division is done with //: 7/2 is 3.
This rounds toward the negative.
Remainders are non-negative.
Regular expressions
Miller lets you use regular expressions (of type POSIX.2) in the following contexts:
In mlr filter with =~ or !=~, e.g. mlr
filter '$url =~ "http.*com"'
In mlr put with sub or gsub, e.g. mlr put
'$url = sub($url, "http.*com", "")'
In mlr having-fields, e.g. mlr having-fields
--any-matching '^sda[0-9]'
In mlr cut, e.g. mlr cut -r -f '^status$,^sda[0-9]'
In mlr rename, e.g. mlr rename -r '^(sda[0-9]).*$,dev/\1'
In mlr grep, e.g. mlr --csv grep 00188555487 myfiles*.csv
Points demonstrated by the above examples:
There are no implicit start-of-string or end-of-string anchors; please
use ^ and/or $ explicitly.
Miller regexes are wrapped with double quotes rather than slashes.
The i after the ending double quote indicates a case-insensitive
regex.
Capture groups are wrapped with (...) rather than
\(...\); use \( and \) to match against parentheses.
For filter and put, if the regular expression is a string
literal (the normal case), it is precompiled at process start and reused
thereafter, which is efficient. If the regular expression is a more complex
expression, including string concatenation using ., or a column name
(in which case you can take regular expressions from input data!), then regexes
are compiled on each record which works but is less efficient. As well, in this
case there is no way to specify case-insensitive matching.
Example:
POKI_RUN_COMMAND{{cat data/regex-in-data.dat}}HERE
POKI_RUN_COMMAND{{mlr filter '$name =~ $regex' data/regex-in-data.dat}}HERE