I'd like to clarify could of things.
"random numbers generated from normal distribution in matlab actually come from standard normal distribution"
This is true only if you use randn If you want to use uniform random numbers then you have to use rand
Non-standard normal random number can be generated as follows:
Uniform random random numbers on a separate interval (not 0-1) between a and b can be generated as follows:
This way you can specify your own range and keep it positive if you like.