RMS of matrices in a cell or array
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Hi all,
If I have an n x n matrix, P, I find the rms by RMS_P = sqrt(mean(Prv(:).^2));.
Please, how can I find the rms of the ith elements in an array, P(;,:,i), along the ith dimension? Thanks.
This is what I have that outputs the rms of a matrix:
ang = 0:90:270;
low_lim = ang - 1;
up_lim = ang + 1;
%The input, inp_file is a 1001 x 1001 matrix, and it's attached.
for i = 1:length(ang)
p_rot = zeros([1001 1001 4]);
ang_var = low_lim + (up_lim - low_lim).*rand(1,length(ang));
p_rot(:,:,i) = imrotate(inp_file,ang_var(i),'crop');
mean_p_rot = mean(p_rot,3);
P = (p_rot(:,:,1)) - mean_p_rot;
P(isnan(P)==1)=0;
RMS_P = sqrt(mean(P(:).^2));
end
I'm trying to repeat this loop multiple times. What I tried is:
for ii = 1: 5
for i = 1:length(ang)
p_rot = zeros([1001 1001 4]);
ang_var = low_lim + (up_lim - low_lim).*rand(1,length(ang));
p_rot(:,:,i) = imrotate(inp_file,ang_var(i),'crop');
mean_p_rot = mean(p_rot,3);
P = (p_rot(:,:,1)) - mean_p_rot;
P(isnan(P)==1)=0;
RMS_P = sqrt(mean(P(:).^2));
end
P_new(:,:,ii) = P;
RMS_P_new(ii) = sqrt(mean(P_new(:).^2));
end
I'm having trouble putting the first loop in another loop, and finding the rms of each ii in P_new(:,:,ii).
Please help. Thanks!
4 Comments
dpb
on 16 Mar 2016
Hmmm....oh, I'd forgotten rms is in Signal Processing toolbox. Try
sqrt(mean(x.*x))
instead or if x can be imaginary
sqrt(mean(x .* conj(x)))
Think should be noticeably faster than .^2.
But, that aside, does rms(P(:)) solve the issue however you compute it?
Answers (1)
John BG
on 17 Mar 2016
Mike
have you noticed that rms has an option to aim on the dimension you want to sweep along?
P=randi(10,3,3,3)
P(:,:,1) =
2.00 8.00 1.00
5.00 10.00 9.00
10.00 7.00 10.00
P(:,:,2) =
7.00 4.00 8.00
8.00 7.00 1.00
8.00 2.00 3.00
P(:,:,3) =
1.00 7.00 1.00
1.00 4.00 5.00
9.00 10.00 4.00
rms(P,1)
ans(:,:,1) =
6.56 8.43 7.79
ans(:,:,2) =
7.68 4.80 4.97
ans(:,:,3) =
5.26 7.42 3.74
rms(P,2)
ans(:,:,1) =
4.80
8.29
9.11
ans(:,:,2) =
6.56
6.16
5.07
ans(:,:,3) =
4.12
3.74
8.10
rms(P,3)
ans =
4.24 6.56 4.69
5.48 7.42 5.97
9.04 7.14 6.45
If you find this answer of any help solving your question, please click on the thumbs-up vote link,
thanks in advance
John
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