MATLAB: Index of a matrix

indexindex of a matrixmatrixsearch

I have two column matricies x and y (neither of them have repeating numbers). I want to search for a number in matrix x, get the index and get the number of that index in matrix y. This seems simple enough to do, but I am still not that familiar with matlab. Can someone help me out please?

Best Answer

index = (x==A); % A is the number you want to find in x.
y(index)

You would probably benefit from spending some time here: http://www.mathworks.com/help/techdoc/learn_matlab/bqr_2pl.html

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MATLAB: Merging two arrays based on index arrays

z_index = [2,3];
y_index = [4,1,5];
z(z_index) = [1,3];
y(y_index) = [-2,4,2];
x(z_index) = z(z_index); % RHS = [1,3]
x(y_index) = y(y_index)  % RHS = [-2,4,2]
x = 1×5
     4     1     3    -2     2
●

Or slightly more robustly:

x = [z(z_index),y(y_index)]; % RHS = [1,3,-2,4,2]
x([z_index,y_index]) = x
x = 1×5
     4     1     3    -2     2
●

MATLAB: Help me with this error!

Instead of:

   y(index) = pi*(x.^2 + 1).^2 *l;

you should write:

   y(index) = pi*(x(index)^2 + 1)^2 *l;

Either that or else you should do:

   y = pi*(x.^2 + 1).^2 *l;

after you exit the for-loop.

As it stands you have a scalar on one side of the equation and a vector on the other side in the original

   y(index) = pi*(x.^2 + 1).^2 *l;

That is what matlab is unhappy about.

Best Answer

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MATLAB: Merging two arrays based on index arrays

MATLAB: Help me with this error!

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