Daniel Hoppe
2004-Jun-30 17:40 UTC
[Rd] AS_NUMERIC and as.numeric - Could someone explain?
Dear List, I stepped into a strange effect which I can't explain to myself (probably due to lack of knowledge on R internals). I have four vectors a,b,c and z of size 10000 each. With these vectors I call .Call("hyp2f1forrey", a, b, b, z, PACKAGE = "hyp2f1") to access SEXP hyp2f1forrey(SEXP a, SEXP b, SEXP c, SEXP x) { int i,n; double *xa, *xb, *xc, *xx, *xresr, *xresi; SEXP resr, resi; n = LENGTH(a); PROTECT(a = AS_NUMERIC(a)); PROTECT(b = AS_NUMERIC(b)); PROTECT(c = AS_NUMERIC(c)); PROTECT(x = AS_NUMERIC(x)); PROTECT(resr = NEW_NUMERIC(n)); PROTECT(resi = NEW_NUMERIC(n)); xa = NUMERIC_POINTER(a); xb = NUMERIC_POINTER(b); xc = NUMERIC_POINTER(c); xx = NUMERIC_POINTER(x); xresr = NUMERIC_POINTER(resr); xresi = NUMERIC_POINTER(resi); for (i = 0; i < n; i++) F77_CALL(hyp)(&xx[i], &xa[i], &xb[i], &xc[i], &xresr[i], &xresi[i]); UNPROTECT(6); return(resr); } I read the documentation in the way that I could either do the call from above or .Call("hyp2f1forrey", as.numeric(a), as.numeric(b), as.numeric(b), as.numeric(z), PACKAGE = "hyp2f1") and remove the PROTECT(a = AS_NUMERIC(a)); PROTECT(b = AS_NUMERIC(b)); PROTECT(c = AS_NUMERIC(c)); PROTECT(x = AS_NUMERIC(x)); in the C-Code. What happens now is that in my resulting vector of length 10000 some values are incorrect depending on the exact way of calling the C-Function. .Call("hyp2f1forrey", a, b, b, z, PACKAGE = "hyp2f1")[11] --> incorrect result .Call("hyp2f1forrey", a[11], b[11], b[11]), z[11]), PACKAGE "hyp2f1") --> works .Call("hyp2f1forrey", as.numeric(a), as.numeric(b), as.numeric(c), as.numeric(z), PACKAGE = "hyp2f1")[11] -- works .Call("hyp2f1forrey", a[1:10000], b[1:10000], b[1:10000]), z[1:10000]), PACKAGE = "hyp2f1") --> works too! Could someone explain to me where the difference in these calls comes from? Thanks in advance, Daniel
Douglas Bates
2004-Jul-01 06:07 UTC
[Rd] AS_NUMERIC and as.numeric - Could someone explain?
AS_NUMERIC in C more closely corresponds to as.double() in R All that as.numeric() in R does is assure that the result is of a numeric mode. It does not coerce integer variables to doubles. Check, for example, str(as.numeric(1:100)) Daniel Hoppe wrote:> Dear List, > > I stepped into a strange effect which I can't explain to myself > (probably due to lack of knowledge on R internals). > > I have four vectors a,b,c and z of size 10000 each. With these vectors I > call > > .Call("hyp2f1forrey", a, b, b, z, PACKAGE = "hyp2f1") > > to access > > SEXP hyp2f1forrey(SEXP a, SEXP b, SEXP c, SEXP x) > { > int i,n; > double *xa, *xb, *xc, *xx, *xresr, *xresi; > SEXP resr, resi; > > n = LENGTH(a); > > PROTECT(a = AS_NUMERIC(a)); > PROTECT(b = AS_NUMERIC(b)); > PROTECT(c = AS_NUMERIC(c)); > PROTECT(x = AS_NUMERIC(x)); > PROTECT(resr = NEW_NUMERIC(n)); > PROTECT(resi = NEW_NUMERIC(n)); > > xa = NUMERIC_POINTER(a); > xb = NUMERIC_POINTER(b); > xc = NUMERIC_POINTER(c); > xx = NUMERIC_POINTER(x); > xresr = NUMERIC_POINTER(resr); > xresi = NUMERIC_POINTER(resi); > > for (i = 0; i < n; i++) > F77_CALL(hyp)(&xx[i], &xa[i], &xb[i], &xc[i], &xresr[i], > &xresi[i]); > UNPROTECT(6); > return(resr); > } > > I read the documentation in the way that I could either do the call from > above or > > .Call("hyp2f1forrey", as.numeric(a), as.numeric(b), as.numeric(b), > as.numeric(z), PACKAGE = "hyp2f1") > > and remove the > > PROTECT(a = AS_NUMERIC(a)); > PROTECT(b = AS_NUMERIC(b)); > PROTECT(c = AS_NUMERIC(c)); > PROTECT(x = AS_NUMERIC(x)); > > in the C-Code. What happens now is that in my resulting vector of length > 10000 some values are incorrect depending on the exact way of calling > the C-Function. > > .Call("hyp2f1forrey", a, b, b, z, PACKAGE = "hyp2f1")[11] --> > incorrect result > .Call("hyp2f1forrey", a[11], b[11], b[11]), z[11]), PACKAGE > "hyp2f1") --> works > .Call("hyp2f1forrey", as.numeric(a), as.numeric(b), as.numeric(c), > as.numeric(z), PACKAGE = "hyp2f1")[11] -- works > .Call("hyp2f1forrey", a[1:10000], b[1:10000], b[1:10000]), > z[1:10000]), PACKAGE = "hyp2f1") --> works too! > > > Could someone explain to me where the difference in these calls comes > from? > > Thanks in advance, > > Daniel > > ______________________________________________ > R-devel@stat.math.ethz.ch mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-devel