I hope you are trying to get the 25 percent of data out of number of data you have. If you have n = 900 datapoint, the following codes might help say you have data is the vector
ndata = size(data, 2) % number of data points
p = 25; percent of data
%compute number of data points you wants
newpoints = floor(ndata*p/100);
%turn row vecror to column vector so that you wont get confused
data = data(:);
newdata = data(1:newpoints); % this will be your new extracted data points
This is the case of one dimensional vector. I hope you can recode for multidimensional in similar way. Good luck Mahesh
