> I have running signal and I need only 100 last data from this signal > and plot it in time..therefore need a matrix with 100 columns to save > this data
OK, my interpretation was wrong...I would call that matrix (while it is one, yes) a [row] vector. So, while circular buffers are wondrous things in some cases, this isn't one in the end as Bruno says.
You will have to do something like
while 1 y(1:end-1)=y(2:end); y(100)=simulationresult(whatever); plot(x,y) ... end
There are many ways to get the same result and as noted above I suggest reading the section under the 2D graphics on 'Animation' to see details of ways to do this that aren't quite as compute-intensive as doing the full plot() all over again.
You can update the [X|YData] vectors instead and then REFRESHNOW for one...