Dear Akshay,
In previous messages, Dirk and I told you that this list was not
the right place for beginner questions. Please stop asking that kind
of questions here.
Best,
Serguei.
Le 21/03/2018 à 09:40, akshay kulkarni a écrit :
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
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