Hello! For calculating the Choleski factor, you should look at: LINPACK: dpofa, dchdc, (dppfa, although i think this one is not included with R) The R code of function chol() is a good starting point. It is located at %RHOME%/library/base/R/base (line 4115 on the windows version of R 1.8.1 patched) LAPACK: dpotrf, dpotf2, dpptrf For matrix inversion you have: LAPACK: dgesv, dposv, dsysv for general, positive definite or symmetric matrices, respectively. For instructions on how to use this subroutines, look at the comments in the code, available at: LINPACK: http://www.netlib.org/linpack/ LAPACK: http://www.netlib.org/lapack/ Good luck! Francisco ----- Mensaje Original ----- De "Liaw, Andy" <andy_liaw at merck.com> Fecha Sat, 28 Feb 2004 08:40:41 -0500 A "'Kosuke Imai'" <kimai at princeton.edu>, r-help at stat.math.ethz.ch Asunto RE: [R] matrix inverse in C In section 5.7 of the `Writing R Extensions' manual, it mentions the interface to numerical linear algebra routines (LINPACK, etc.). You will need to figure out which are the ones you need and how to call them. As these are expressed as Fortran routines, you can call them from C using the F77_CALL() macro mentioned in that manual. I believe many would say that routines in Numerical Recipes are not really `industrial strength'... HTH, Andy
From: Kosuke Imai Hi, I'm writing an R package using the C code i've written. I'm wondering if anyone knows an easy way to calculate an inverse and cholesky factor of a matrix using the Fortran/C library of R: and how to call them from C. My code is based on the Numerical Reciepe code, and I'm trying to use something that is already in R. Thanks for your help in advance, Kosuke --------------------------------------------------------- Kosuke Imai Office: Corwin Hall 041 Assistant Professor Phone: 609-258-6601 (Direct) Department of Politics Fax: 609-258-1110 (Department) Princeton University Email: kimai at Princeton.Edu Princeton, NJ 08544-1012 http://www.princeton.edu/~kimai