How to make a random vector in Matlab as a ones and zeros but under control?

How to make a random vector in Matlab as a ones and zeros with this condition, that the number of ones be under my control. which it means i want the random vector with fix number of ones but totally random in positions. for example: this line will make a random number 0 and 1 also it's totally random in the vector but i cannot control number of 1 and 0 e.g i need number of 1 be 90 and the rest 0 or any other number V1=round(rand(1,256));

Answer 1

[Thorsten]

 r = zeros(1,256);
 r(randperm(256, 90)) = 1;

[Hamid Reza Barzegar]

Thank you. it seems working. i should try it in the main program.