get coordinates for bar-plotting
[xb yb]=ebar(y[,barWidth[,barNumber,clusterSize,[,x]])
y :
vector of y-data
barWidth :
x-size of bars
if barWidth=0 then autosize
default: barWidth=0
barNumber :
number whithin the cluster
clusterSize :
total number of bars in one cluster
x :
vector of x-data
xb :
vector of x-coodinates
yb :
vector of y-coodinates