# sum of rand matrix equal to zero

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Offroad Jeep on 5 May 2015
Commented: Offroad Jeep on 17 May 2016
Dear All,
I want to generate matrix A ,i.e. n by n random matrix but the sum(sum(A)) = zero. Help in this regard will be highly appreciated........
Regards..........

Hooman Habibi on 5 May 2015
Subtract the mean from the samples:
n=10; z=randn(n,n); z=z-sum(sum(z))/(n*n); sum(sum(z))
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Offroad Jeep on 17 May 2016

### More Answers (2)

Bus141 on 5 May 2015
Edited: Bus141 on 5 May 2015
The command randn pulls from a normal distribution with distribution N(0,1), implying with a large enough sample the mean should be zero. The sum of all dimensions should also converge toward zero since the values above and below the mean will cancel each other out, as they have equal probability.
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Offroad Jeep on 17 May 2016

Michael Haderlein on 5 May 2015
What kind of random distribution do you want? Here I use normal distribution, for other distributions just replace randn by the respective function:
n=100;
A=randn(100);
B=A-mean(A(:));
sum(B(:))
ans =
3.8913e-13
That's not exactly zero, but you'll not easily come close due to numerical precision.
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Offroad Jeep on 17 May 2016