How to sample in matlab by multinomial distribution?

I know for a random variable x that P(x=i) for each i=1,2,...,100. Then how may I sample x by multinomial distribution, based on the given P(x=i) in matlab?

I am allowed to use matlab build in commend

rand

and

randi

but not

mnrnd.

Thank you!

[James Tursa]

What have you done so far?

[dragoon]

I use

t = cmusum(P)

command to compute the cdf of P(x=i). Then I use

rand

to find a number between (0,1), and find for what i that t(i)>rand. Then I output x(i).

This is my impression for sampling with a distribution. But I am not sure this is sampling with mutinoimal distribution...