Change 1 to -1 in a matrix

Hi to all the members, I have a 4 X 4 Matrix of one i.e ones(4). I want to change all the elements from 1 to -1 randomly in the matrix. BUT Only one element should change at a time from 1 to -1. That it the 1 changes to -1 sixteen times as we have sixteen elements in the matrix.

Answer 1

[Adam]

m = ones(4);
r = rand(4) - 0.5;
m = m .* sign( r );

is one of many ways to do it.

[Offroad Jeep]

Thanks for reply......Kindly see the question as i left some idea what i needed

[Adam]

orderIdx = randperm(16);

for n = 1:16
   m( orderIdx(n) ) = -1;
end

Answer 2

[KSSV]

A = ones(4,4) ;
N = 5 ;  % number of ones to make negative 
idx = randsample(1:16,N) ;  % select N random positions to change 1 to -1
A(idx) = -1 ;

[Offroad Jeep]

Thanks for reply......Kindly see the question as i left some idea what i needed

[KSSV]

A = ones(4,4) ;
pos = 1:16 ;
for i = 1:16
    idx = randsample(pos,1) ;
    A(idx) = -1 ;
    pos = setdiff(pos,idx)  ;
end

[Offroad Jeep]

giving error as one 1 remains unchanged.... can please go through... regards

[KSSV]

At the end:

A(pos) = -1 ;