Displaying 3 results from an estimated 3 matches for "postmultiplying".
2003 May 08
2
natural splines
...is is this too obscure for R-help.
In package splines, ns(x,,knots,intercept=TRUE) produces an n by K+2
matrix N, the values of K+2 basis functions for the natural splines with K
(internal) knots, evaluated at x. It does this by first generating an
n by K+4 matrix B of unconstrained splines, then postmultiplying B by
H, a K+4 by K+2 representation of the nullspace of C (2 by K+4), which
contains the 2nd derivatives of the unconstrained splines evaluated at
the boundary knots. E.g. see Hastie and Tibshirani, Generalized Additive
Models, exercise 2.5, p36. The QR decomposition is used to get H.
This can p...
2007 Jan 23
3
[fixed] vectorized nested loop: apply a function that takes two rows
(Extremely sorry, disregard previous email as I hit send before pasting the latest version of the example; this one is smaller too)
Dear R users,
I want to apply a function that takes two vectors as input to all pairs
(combinations (nrow(X), 2))of matrix rows in a matrix.
I know that ideally, one should avoid loops in R, but after reading the docs for
do.call, apply, etc, I still don't know
2007 Jan 23
3
[fixed] vectorized nested loop: apply a function that takes two rows
(Extremely sorry, disregard previous email as I hit send before pasting the latest version of the example; this one is smaller too)
Dear R users,
I want to apply a function that takes two vectors as input to all pairs
(combinations (nrow(X), 2))of matrix rows in a matrix.
I know that ideally, one should avoid loops in R, but after reading the docs for
do.call, apply, etc, I still don't know