[Rcpp-devel] List of Lists to List of Vectors
A slightly improved version:
library(Rcpp)
code = '
SEXP test(List a)
{
auto l = Rf_length(a[0]);
using svec = std::vector<SEXP>;
std::vector<svec> x(l);
for (List b : a)
{
if (b.size() != l)
stop("Ragged input");
for (int i = 0; i != l; ++i)
x[i].push_back(b[i]);
}
return wrap(x);
}'
f = cppFunction(code = code, plugins = "cpp11")
res = lapply(f(list(list(T, 1, 'a'),
list(F, 2, 'b'))),
unlist)
On Sun, May 3, 2015 at 11:57 AM, Tim Keitt <tkeitt at utexas.edu> wrote:
Here's a really bare-bones version. Not very pretty or complete, but it
does do the job. Could the 'unlist' part be converted to Rcpp?
THK
library(Rcpp)
code = '
SEXP test(List a)
{
int l = Rf_length(a[0]);
typedef std::vector<SEXP> svec;
std::vector<svec> x(l);
for (int i = 0; i != l; ++i)
for (int j = 0; j != a.size(); ++j)
{
List b = a[j];
x[i].push_back(b[i]);
}
return wrap(x);
}'
f = cppFunction(code = code)
res = lapply(f(list(list(1, 'a'), list(2, 'b'))), unlist)
On Sat, May 2, 2015 at 1:18 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
On 2 May 2015 at 10:49, William Dunlap wrote: | Since translation from R to Rcpp is "seamless" I will leave that to you. One problem is with the strongly typed nature of C++. Rearranging dynamicly growing objects can be done. I think I used Boost's variant type a few years. I am sure there are other possibilities. We should collect a few and compare. But in C++ please :) Dirk -- http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
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