Rcpp + inline - 创建和调用附加函数 [英] Rcpp + inline - creating and calling additional functions

问题描述

我想知道是否可以使用 main 函数中的 inline 包来创建 Rcpp 函数.这是我想要做的一个例子:

I would like to know if there is a way to create Rcpp functions using the inline packages within the main function. This is an example of what I want to do:

library(inline)
library(Rcpp)
a = 1:10
cpp.fun = cxxfunction(signature(data1="numeric"), 
                      plugin="Rcpp",
                      body="
int fun1( int a1)
{int b1 = a1;
 b1 = b1*b1;
 return(b1);
}

NumericVector fun_data  = data1;
int n = data1.size();
for(i=0;i<n;i++){
fun_data[i] = fun1(fun_data[i]);
}
return(fun_data);
                           ")

这应该导致:

> cpp.fun(a)
[1]  1  4  9  16  25  36  49  64  81  100

但是我知道编译器不会接受在 main 方法中创建您自己的函数.我将如何使用 inline 创建和调用另一个 Rcpp 函数而不必将其传递给 R?

however I know that the compiler will not accept the creation of your own function within the main method. How will I go about creating and calling another Rcpp function with inline without having to pass it through to R?

推荐答案

body 是针对函数体的，要查看includes参数的<代码>cxx函数:

body is for the body of the function, you want to look at the includes argument of cxxfunction:

library(inline)
library(Rcpp)
a = 1:10
cpp.fun = cxxfunction(signature(data1="numeric"), 
                      plugin="Rcpp",
                      body='

IntegerVector fun_data  = data1;
int n = fun_data.size();
for(int i=0;i<n;i++){
    fun_data[i] = fun1(fun_data[i]);
}
return(fun_data);
', includes = '

int fun1( int a1){
    int b1 = a1;
    b1 = b1*b1;
    return(b1);
}

' )    
cpp.fun( a )

?cxxfunction 有关于它的 includes 参数的详细文档.

?cxxfunction has detailed documentation about its includes argument.

但请注意，此版本将在您的输入向量中进行适当的修改，这可能不是您想要的.另一个同样利用 Rcpp 版本的 sapply 的版本:

But note that this version will make in place modifications in your input vector, which is probably not what you want. Another version that also takes advantage of Rcpp version of sapply:

library(inline)
library(Rcpp)
a = 1:10
cpp.fun = cxxfunction(signature(data1="numeric"), 
                      plugin="Rcpp",
                      body='

IntegerVector fun_data  = data1; 
IntegerVector out = sapply( fun_data, fun1 ) ;
return(out);
', includes = '

int fun1( int a1){
    int b1 = a1;
    b1 = b1*b1;
    return(b1);
}

' )    
cpp.fun( a )
a

最后，您绝对应该看看 sourceCpp.有了它，您可以在 .cpp 文件中编写代码，其中包含:

Finally, you definitely should have a look at sourceCpp. With it you would write your code in a .cpp file, containing:

#include <Rcpp.h>
using namespace Rcpp ;

int fun1( int a1){
    int b1 = a1;
    b1 = b1*b1;
    return(b1);
}

// [[Rcpp::export]]
IntegerVector fun(IntegerVector fun_data){ 
    IntegerVector out = sapply( fun_data, fun1 ) ;
    return(out);
}

然后，您只需 sourceCpp 您的文件并调用该函数:

And then, you can just sourceCpp your file and invoke the function :

sourceCpp( "file.cpp" )
fun( 1:10 )
#  [1]   1   4   9  16  25  36  49  64  81 100

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