How can I create a gaussian filter without imfilter ,fspecial or conv2

 I=imread(image);
 h=fspecial('gaussian',si,sigma);
 I=im2double(I);
 I=imfilter(I,h,'conv');
 figure,imagesc(I),impixelinfo,title('Original Image after Convolving with gaussian'),colormap('gray');

[David Young]

Any image processing or computer vision textbook will give you the formulae, as indeed will Wikipedia. Just code them into ordinary MATLAB. But why not use imfilter etc.? Much easier.