411 REFERENCE · Wikibooks
Linear Algebra and the C Language/a0oa
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The sum of the eigenvalues of A is equal to the trace of A:
Copy/Paste into the octave window
% The sum of the eigenvalues of A is equal to the trace of A:
clear, clc
n = 4;
A = round(10*randn(n)); %% A matrix nxn
A = A'*A %% A symetric matrix
% Eigenvalues
Evalues = eigs(A)
printf ("Add up all the eigenvalues: sum(Evalues)\n\n")
SEvalues = sum (Evalues)
printf ("\nCompute the trace: trace(A)\n\n")
traceA = trace(A)
%%
Screen output example:
A =
658 111 -53 221
111 113 -16 -4
-53 -16 86 116
221 -4 116 330
Evalues =
783.4492
309.8050
87.2533
6.4926
Add up all the eigenvalues: sum(Evalues)
SEvalues = 1187.0
Compute the trace: trace(A)
traceA = 1187
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