Hello Natacha,
the function unifrnd actually calls rand. If a and b are the two first arguments of unifrnd, and r is the output of unifrnd, what unifrnd does is:
a2 = a/2;
b2 = b/2;
mu = a2+b2;
sig = b2-a2;
r = mu + sig .* (2*rand(sizeOut,'like',mu)-1);
Of course there are some error checks as well.
Type the following command in the MATLAB command window to take a look of the code: >>edit unifrnd
Of course they are few other differences in terms of usage (syntax). You can find more information from help documentation. https://www.mathworks.com/help/stats/unifrnd.html?searchHighlight=unifrnd&s_tid=doc_srchtitle https://www.mathworks.com/help/matlab/ref/rand.html?searchHighlight=rand&s_tid=doc_srchtitle
Another difference is that unifrnd is accessible when you have installed Statistics and Machine Learning Toolbox.
