calculation of first order histogram

how to find first order histogram by

The first-order histogram P(I) is defined as: number of pixels with gray level I/total number of pixels in the region

from this i have to find mean ,standard deviation etc,

i can find those ,but plz tell how to calculate first order histogram

Answer 1

[Image Analyst]

I know it sounds obvious, but did you try hist()?

[counts, binCenters] = hist(data);
P = counts/sum(counts);
meanValue = (counts .* binCenters) / sum(counts);

I presume you know how to get SD from the histogram.