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I am looking for a certain operation that makes a 1 tensor from a 2 tensor by filtering out only the diagonal elements.

For instance,

(f1g1 f1g2 f1g3)

(f2g1 f2g2 f2g3)

(f3g1 f3g2 f3g3)

becomes

(f1g1)

(f2g2)

(f3g3)

after a certain operation.

What operation could I use?

Thanks a million for the one who can help me out here.

Dirk

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# Selecting diagonal elements from a matrix to make a vector

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