How can i reshape a matrix to my preferred dimension and discard the excess element

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Cutie am 5 Jul. 2021
Kommentiert: Cutie am 7 Jul. 2021
I have a signal whose size is 48640 but I want to reshape it using window size 512,1024,..etc but the
fl = 512 % window size
X_data2 = reshape (signal, fl, []) % i want a matrix whose row is equal to window size fl
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Walter Roberson am 7 Jul. 2021
The problem is not finding some way to plot the matrix. The problem is finding a way to plot to have clear information. It seems to me that the kind of information you are working with does not have a clear interpretation.
Consider for example if you take
x = rand(72,1);
x1 = sort(x);
plot([x,x1])
legend({'x', 'x1'})
x and x1 have the same mean, but it is highly likely that the interpretation of x and x1 should be very different.
But now for example,
x2 = reshape(reshape(x, 2, []).',[],1);
plot([x,x2])
Nearly the same but every pair has been exchanged, but if this was your measured features, then what would be the implication of this compared to the other one?
Or if the first entry of x1 (the sorted one) were decreased by 0.05 and the last five entries were increased by 0.01 each, the sort order would remain the same, and the mean would stay the same, but what would it mean ???
When you have 72 values, then what is the significance of the 11'th or 48'th being different ?
You can plot, yes, but humans are often pretty bad at immediately being able to figure out from a graph what it means for individual components to be particular values. So I do doubt that you can plot in a way that gives you clear information.
Cutie am 7 Jul. 2021
@Walter Roberson, thank you for the explanation. This is truly appreciated.

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Akzeptierte Antwort

Walter Roberson am 5 Jul. 2021
X_data2 = buffer(signal(:,1), fl)
This will create columns from the first channel of signal, with each column being fl samples long. As many columns will be needed as necessary. If the signal is not an exact multiple of fl then the last column will be 0 padded.
This requires the Communications Systems Toolbox.
It is one of the utility functions that I think really should be moved to basic MATLAB.
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Cutie am 6 Jul. 2021
This works. Thank you.

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Weitere Antworten (2)

Srijan Jain am 5 Jul. 2021
Hey
I understand that you are trying to remove the excess elements of a matrix. You may want to try:
childarray=parentarray(startrow:endrow, startcol:endcol);
Hope this helps
Srijan
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Cutie am 6 Jul. 2021
Can please explain further. When I tried it, the row work okay but the column is giving error as follows:
childarray=signal2(1:fl, 1:3); % but with error index in postition 2 excees array bounds (must not exceed 1). When I make the col side 1:1, I has as 8192 x 1 matrix

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Yongjian Feng am 5 Jul. 2021
What is the original matrix you want to reshape? Is it signal?
reshaped = signal(1:fl, :)
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Cutie am 6 Jul. 2021
This only output an fl by 1 matrix.

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