dear serguei, I have another question:
If M is a matrix, M.nrow() should return the number of rows...but I encountered the following inconsistency: > M x y z [1,] 1 0 0 [2,] 4 3 0 [3,] 3 1 1 [4,] 2 90 87 [5,] 9 76 23 [6,] 5 23 13 > cppFunction('IntegerVector tccp5(IntegerMatrix M) { int x = M.nrow(); return > x;}') > tccp5(M) [1] 0 0 0 0 0 0 can you please explain what is happening( I am very new to Rcpp and C++)? very many thanks for your time and effort... yours sincerely, AKSHAY M KULKARNI ________________________________ From: Serguei Sokol <serguei.so...@gmail.com> Sent: Tuesday, March 20, 2018 7:26 PM To: akshay kulkarni; Rcpp R Subject: Re: [Rcpp-devel] how to reference a row of a matrix in C++ in Rcpp Le 20/03/2018 à 12:10, akshay kulkarni a écrit : > dear members, > > I came to know from stackoverflow that the > following references a row in a matrix in C++: > > M[2] references 2nd row of the Matrix. SO is too big to check this assertion by ourself. Do you have a link? > > > I am using Rcpp to write C++ code in R. > > > However, I ended up with the following inconsistency: > > > M > x y z > [1,] 1 1 1 > [2,] 2 2 2 > [3,] 3 3 3 > [4,] 4 4 4 > [5,] 5 5 5 > [6,] 6 6 6 > > cppFunction('IntegerVector tccp3(IntegerMatrix M) { IntegerVector x = > M[2]; return x;}') Try cppFunction('IntegerVector tccp3(IntegerMatrix M) { IntegerVector x = M(2,_); return x;}') Best, Serguei. > > tccp3(M) > [1] 0 0 0 > > cppFunction('IntegerVector tccp4(IntegerMatrix M) { IntegerVector x = > M[1]; return x;}') > > tccp4(M) > [1] 0 0 > > tccp3 should return (3,3,3) and tccp4 should return (2,2,2). Can you please > shed light on what is going on? > > very many thanks for your time and effort.... > > Yours sincerely, > AKSHAY M KULKARNI > > > > _______________________________________________ > Rcpp-devel mailing list > Rcpp-devel@lists.r-forge.r-project.org > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel Rcpp-devel Info Page<https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel> lists.r-forge.r-project.org Discussion list for Rcpp, RInside and various packages using Rcpp or RInside. This list is subscriber-only, in other words in order to post to the list you must be ... >
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