MATLAB: I have 30×30 matrix and need to extrapolate lower triangle numbers

extrapolatelower triangle

I need to pull out everything below the diagonal (the lower triagnle numbers), but I don't want to use tril and change the diagonal and upper triangle to zeros. I just want to pull out the lower triangle numbers so that I can make a vector out of its values.
Anything is helpful!! Thank you!

Best Answer

You just want to extract the lower triangle, whatever is in it? The result going into a vector?
A = magic(5) - 10
A =
     7    14    -9    -2     5
    13    -5    -3     4     6
    -6    -4     3    10    12
     0     2     9    11    -7
     1     8    15    -8    -1
     
V = A(logical(tril(ones(size(A)))))
V =
     7
    13
    -6
     0
     1
    -5
    -4
     2
     8
     3
     9
    15
    11
    -8
    -1
That includes the diagonal. But if you want the strictly lower triangle, just set a second argument for tril.
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