The script command sortmap is used to sort matrices in more complex ways than simply ascending or descending order of the array. It is used to create a map of the sorted indices of the array that can be reused afterwards to sort the original matrix or other matrices.
This function was introduced in the 2018a R6 release.
Syntax |
Description |
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out = sortmap(A); |
Returns a matrix of indices that map the sorted matrix of A. Complex values are sorted by magnitude and then by angle. A is treated as a linear array for sorting, but out preserves the shape of A. Typically the command is used for Nx1 or 1xN matrices. |
out = sortmap(A, ascending); |
The optional bool argument is set to true by default. When it is false, the sort is done in descending order. |
Example
This example shows how to use sortmap instead of sort, and that the results are equivalent
A = [3; 4; 1; 7; 10; -1]; ?B = sort(A); m = sortmap(A); ?D = A(m);
This example shows how to sort by ascending imaginary part, real part or magnitude
A = [3+1i; 4+0.1i; 1-10i; 7-20i; 10+15i; -1+0i]; m = sortmap(imag(A)); ?B = A(m); # sorted by ascending imaginary part m = sortmap(real(A)); ?D = A(m); # sort by ascending magnitude m = sortmap(abs(A)); ?E = A(m); # sort by ascending magnitude
This example shows how 2 different vectors (neff and ng) can be sorted according to descending neff.
neff = [2.3; 2.4; 3.2; 1.45 ]; ng = [4.2; 4.3; 4.8; 4.9 ]; m = sortmap(neff,false); ?neff = neff(m); ?ng = ng(m);
This example shows how we can sort 2 vectors of x and y by the closest points to x0,y0
x = [4.3; -4; -2; 10; 2.0 ]; y = [ -1; 1; 2; 5; -4 ]; x0 = 2; y0 = 2; m = sortmap( (x-x0)^2 + (y-y0)^2); x = x(m); y = y(m); ?[x,y];
This example shows how the rows of an NxM matrix can be sorted based on the values in the 3rd column:
A = [ 2, 4, 6; 3, 2, 1; 4, 4, 4 ]; m = sortmap(A(:,3)); ?A = A(m,:);
See Also