Retrieving histogram of greyscale image in MATLAB (without imhist() and histogram() functions).

Histogram.m

clc;
clear;
clf;

Image = rgb2gray(imread("peppers.png"));

Bins = zeros(256,1);
for Intensity = 0: 255
    Bins(Intensity+1) = nnz(Image == Intensity);
end

plot((0:255),Bins);
xlabel("Pixel Intensity"); ylabel("Number of Occurences");