Hello, Also, R uses doubles, not floats.
Hope this helps, Rui Barradas Em 24-09-2012 23:27, Peter Langfelder escreveu:
Erin, you seem to confuse R and C syntax a bit, among other things. See below. On Mon, Sep 24, 2012 at 3:03 PM, Erin Hodgess <erinm.hodg...@gmail.com> wrote:Dear R People: I'm working on a project that will pass a matrix from an R function to a C subroutine. I tried to write the following: #include<R.h> #include<Rinternals.h> void lu1(int *n, float *a, float *b, float *ab) { int i,k,j,p,na=*n+10; float sum, l[200][200],u[200][200]z[200];Comma missing?for(i=0;i<na;i++) { for(j=0;j<na;j++) { l[i,j]=0.0; u[i,j]=0.0;In C you must write l[i][j] and u[i][j]. l[i,j] is actually equal to l[j] and that's an array of 200 doubles.} z[i] =0.0; } //********** LU decompositio*n *****// for(k=1;k<=*n;k++) { u[k][k]=1; for(i=k;i<=*n;i++) { sum=0; for(p=1;p<=k-1;p++) sum+=l[i][p]*u[p][k]; l[i][k]=a[i][k]-sum;a is a single-index array. You cannot index it using two indices. Convert the two into one using something like i*dimension + k. Same below. HTH, Peter} for(j=k+1;j<=*n;j++) { sum=0; for(p=1;p<=k-1;p++) sum+=l[k][p]*u[p][j]; u[k][j]=(a[k][j]-sum)/l[k][k]; } } //***** FI*NDI*NG Z; LZ=b*********// for(i=1;i<=*n;i++) { //forward subtitutio*n method sum=0; for(p=1<i;p++) sum+=l[i][p]*z[p]; z[i]=(b[i]-sum)/l[i][i]; } //********** FI*NDI*NG X; UX=Z***********// for(i=*n;i>0;i--) { sum=0; for(p=*n;p>i;p--) sum+=u[i][p]*ab[p]; ab[i]=(z[i]-sum)/u[i][i]; } } And here is the output: R CMD SHLIB lu1.c gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -fpic -O3 -pipe -g -c lu1.c -o lu1.o lu1.c: In function ‘lu1’: lu1.c:15:8: error: incompatible types when assigning to type ‘float[200]’ from type ‘double’ lu1.c:16:8: error: incompatible types when assigning to type ‘float[200]’ from type ‘double’ lu1.c:33:25: error: subscripted value is neither array nor pointer nor vector lu1.c:41:26: error: subscripted value is neither array nor pointer nor vector make: *** [lu1.o] Error 1 erin@ubuntu:~$ I'm thinking that the matrix is hanging things up. Does this look familiar, please?______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
