Equivalent of inc(x) or x++ in R

Let try different solutions to mimic C operand ++ to have the most efficient.



n <- as.integer(1)
system.time(for (i in 1:100000) n <- n + 1)

 n <- as.numeric(1)
system.time(for (i in 1:100000) n <- n + 1)

 n <- as.double(1)
system.time(for (i in 1:100000) n <- n + 1)

No change:
utilisateur     système      écoulé 
      0.035       0.000       0.036 

Not let do a function inc():

inc <- function(x) eval.parent(substitute(x <- x + 1))

n <- as.integer(1)
system.time(for (i in 1:100000) inc(n))

It is ten times slower:
utilisateur     système      écoulé 
      0.470       0.005       0.477 

Using the Hmisc package:
require(Hmisc)
n <- as.integer(1)
system.time(for (i in 1:100000) inc(n) <- 1 )

It is only 3 times slower:
utilisateur     système      écoulé 
      0.150       0.001       0.151 

And using a C function:
In file inc.c:
#include <R.h>
void inc(int *x)
{
    x[0]++;
}

Enter these in R console:
system('R CMD SHLIB inc.c')
dyn.load("inc.so")

n <- as.integer(1)
system.time(for (i in 1:100000) n <- .C("inc", n=n)$n)

The result is the worst of all the tries !
utilisateur     système      écoulé 
     31.783       3.996      36.163 

In conclusion n <- n + 1 is still the best !

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