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  1. What do Q and R stand for?

  2. Why must the diagonal entries of R be positive instead of just nonzero?

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$A=QR$, $Q$ is an orthogonal matrix and $R$ is an upper triangular matrix. –  Mhenni Benghorbal Nov 28 '12 at 6:48
Thanks. I know that. I mean what names do Q and R stand for? Queer Rainbow? Quixotic Renegade? –  gondonla Nov 28 '12 at 7:02
See here under "computing the $QR$ decomposition" and you will find the answer for part $(2)$ of your question. –  Mhenni Benghorbal Nov 28 '12 at 7:50
+1 for "what do Q and R stand for". My guess was that ORthogonal starts with O and tRiangulaR ends with R, but OR is a logical operator so they call it QR. Alternatively QR are two subsequent letters and M (matrix), n (count) and P (often used in definitions here) are used. In that case you would start namefinding from LU. –  naxa Jan 30 '13 at 14:28

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