Matrix dimensions must agree!!

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Emmanuel
Emmanuel on 13 Oct 2014
Answered: Ganesh P. Prajapat on 11 Jun 2016
Dear all,
I am preparing a matlab simulation to plot the output of an SMI adaptive beamformer algorithm, but i keep getting "matrix dimensions must agree" response, and i'm new to matlab and have not been able to fix this issue.
I am kindly asking for assistance.
Many thanks.
Here is the code:
N = 7;
l = 0:N-1;
fs = 12e6;
f = 1e6;
fi = 1e3;
SNR = 0;
INR = 10;
m = 8;
c = physconst('LightSpeed');
lambda = c/f;
d = lambda/2;
angles = -90:1:90;
theta = ([-pi/2,pi/2]);
phi = ([-pi,pi]);
j= sqrt(-1);
noisePwr = 0.5; % noise power
Ps = noisePwr*SNR; % signal power
A = Ps*10^(SNR/20);
I = 10^(INR/20);
s = A*exp(j*2*pi*f/fs*l);
i = I*exp(j*2*pi*fi/fs*l);
n = sqrt(noisePwr/2)*randn(m,l)+j*randn(m,l);
k = (2*pi)/lambda;
S = s';
a = exp(-j*2*pi*d*(0:m-1)'*sind(angles));%steering matrix
B = ctranspose(a);
input = a*S;
X = input + i + n;
r= (X*ctranspose(X))/N;
R = inv(r);
alpha = inv(B*R*a);
w = alpha*R*a; % weight vector
W = ctranspose(w);
Y = W*X;
plot (Y)
  3 Comments
Emmanuel
Emmanuel on 14 Oct 2014
This is the error i'm getting in line 27.
Warning: Size inputs must be scalar. This will error in a future release. > In New at 22 Warning: Size inputs must be scalar. This will error in a future release. > In New at 22 Error using * Inner matrix dimensions must agree.
Error in New (line 27) input = a*S;
Stephen23
Stephen23 on 14 Oct 2014
An Aside: don't use i, j and input as variable names, as these are the names of inbuilt functions in MATLAB. You can use which to identify any existing functions, or help for more information on these specific functions.

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Answers (3)

Ganesh P. Prajapat
Ganesh P. Prajapat on 11 Jun 2016
in line 27.. it should be >>input = a.*S as it requires term by term multiplication

Image Analyst
Image Analyst on 13 Oct 2014
Paste in ALL the red error text, don't snip out small chunk of it like you did. Most likely something is a vector or array that you thought was a single scalar number. Or you're using * to do a matrix multiply instead of .* to do an element-by-element multiply.
  1 Comment
Image Analyst
Image Analyst on 14 Oct 2014
And what is the size of a and of S? Do this:
whos a
whos S
if a is m by n, then S must be n by p - the n's must be the same, that's just basic matrix math.
You might also look at this: http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/ so you can solve these things yourself LOTS faster. Debugging by Answers forum always takes longer.

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Stephen23
Stephen23 on 13 Oct 2014

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