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Matrix indexing and plotting related doubt.

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Anshuman S
Anshuman S on 13 Jun 2018
Commented: Anshuman S on 18 Jun 2018
I am having a 3D matrix with 20 rows (x direction) , 50 cols (y direction) and 187 points ( z direction ,3rd dimension ). I want to view the plane described by x = 3 . i.e the the z-y plane at x= 3.
I have used the syntax
disp(A(3,:,:)) ;
but it's showing the result as (:,:,35115) cols 1 through 50 etc. what I want is the 50 cols with 187 points each .
Also I want to ask that, how can I plot a single column of a 3D matrix. example A(5,4,:) this will be a set of points ( 187 points ) in the z-direction. I want to plot these points only .

Answers (1)

per isakson
per isakson on 13 Jun 2018
It seems as if you need to use squeeze to get a 2D matrix
mat = zeros( 20, 50, 187 );
len = numel( mat );
mat = reshape( (1:len), size(mat) );
imagesc( squeeze( mat(3,:,:) ) )
disp( squeeze( mat(3,:,:) ) )
See also: Exploring Volumes with Slice Planes in the documentation


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Anshuman S
Anshuman S on 16 Jun 2018
Yes , the color contrast is not correct. I guess, The intensity of the color depicts the magnitude of the value inside the cell of the matrix. But it''s not according to the magnitude there.
per isakson
per isakson on 16 Jun 2018
Regarding the picture
  • The x-axis is too long; the length is 187 rather than 181. Thus, I suspect the size of C used to produce the picture is not the size that you report, 22x24x181
  • You should take a second look at the code that you used. The values of the plotted variable, mat, are not those of your C. The values are created according to my original example, i.e. (1:len). The picture of my answer didn't show zeros( 20, 50, 187 ). You need to understand the code you use!
  • You didn't try imagesc( squeeze( C(15,:,:) ) ) as I proposed. Thus, I propose you do it now.

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