MATLAB: Finding x value for given y in a zig-zag data.

finding x valuesMATLAB

I have a data which oscillates around x-axis. How can I get x values for a given y value. I can get as many, I will sort the one required.

Thank you.

Best Answer

Use findpeaks (with the original and negative of your data), or islocalmax and islocalmin, to get the peaks and valleys, then for each of those segments, use interp1 to get the x-values for a y-value in each segment.

This obviously requires a loop. There is no alternative.

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MATLAB: I have X vector and Y vector. I have plotted graph. Now I sorted out some peak values (from Y). Stored in pks. Now, corresponding to these peaks values(pks), how I can find its corresponding X values

If there is a biunivocal correspondence between X and Y (i.e. to each value of X corresponds only one value of Y and vice versa), then:

xpks = zeros(numel(pks),1);
for i = 1:numel(pks)
  xpks(i) = pks(find(Y == pks(i),1));
end

MATLAB: Create sparse matrix with zig-zag diagonal

You could use sparse(), building appropriate vectors of indices and values, e.g.:

 nCol = size(A, 2) ;
 nRow = nCol * size(A, 1) ;
 I = (1:nRow).' ;
 J = reshape(repmat(1:nCol, size(A, 1), 1), [], 1) ;
 B = sparse(I, J, A(:), nRow, nCol) ;

(that you can write in two lines actually, but I wanted to keep it clear)

Best Answer

Related Solutions

MATLAB: I have X vector and Y vector. I have plotted graph. Now I sorted out some peak values (from Y). Stored in pks. Now, corresponding to these peaks values(pks), how I can find its corresponding X values

MATLAB: Create sparse matrix with zig-zag diagonal

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