MATLAB: Matrix with alternating signs in each row vector

matrix

Hi Guys,
Is there a way to improve on this code that I wrote to optimize it?
M = zeros(M,N); % create an MxN matrix 
M(1,:) = 1;  % Set first row to 1
for r = 2:I
    M(r,:) = -M(r-1,:);   %sets alternate rows to -1 and +1
end
a = M * diag(1 2 3 4 5);
so M creates:
M =
     1     1     1     1     1
    -1    -1    -1    -1    -1
     1     1     1     1     1
    -1    -1    -1    -1    -1
     1     1     1     1     1
    -1    -1    -1    -1    -1
     1     1     1     1     1
    -1    -1    -1    -1    -1
and a
a =
     1     2     3     4     5
    -1    -2    -3    -4    -5
     1     2     3     4     5
    -1    -2    -3    -4    -5
     1     2     3     4     5
    -1    -2    -3    -4    -5
     1     2     3     4     5
    -1    -2    -3    -4    -5
Is this the fastest and most efficient implementation to get the above? Thanks!

Best Answer

Some improvement.
m=5;n=4;
M=ones(m,n);
M(2:2:end,:)=-1
Or alternative:
m=9;n=8;
a=(2*mod((1:m)',2)-1)*(1:n)
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