Converting ascii text into (floating-point) numeric values is a very common problem. The fast_float header-only C++ library by Daniel Lemire does this very well, and very fast at up to or over to 1 gigabyte per second as described in more detail in a recent arXiv paper.
This package brings this header-only library to R so that other R user can access it simply by adding LinkingTo: RcppFastFloat.
A modified example function is included, try
with default arguments—or supply some arguments. We also include a simple timing comparison in the file benchmark/comparison.R which you can run just call via Rscript or r. On our machine, fast_float comes out as just over 3 times as fast as the next best alternative (and this counts the function calls and all, so pure parsing speed is still a little bettter).
> source("comparison.R")
Unit: milliseconds
expr min lq mean median uq max neval cld
scanf 218.8936 224.1223 238.5650 227.1901 229.9116 1343.433 100 c
atof 124.8087 127.3274 129.4104 128.5858 130.9138 146.334 100 b
strtod 124.5705 127.2157 129.1238 129.1042 130.7504 137.143 100 b
stod 127.1751 129.7343 131.7339 131.4854 133.1425 147.763 100 b
fastfloat 40.6219 41.3042 42.5729 42.3209 43.1738 57.788 100 a
> Or in chart form:
Right now the package is brand new and reasonably empty.
Any problems, bug reports, or features requests for the package can be submitted and handled most conveniently as Github issues in the repository.
Before submitting pull requests, it is frequently preferable to first discuss need and scope in such an issue ticket. See the file Contributing.md (in the Rcpp repo) for a brief discussion.
For the R package, Dirk Eddelbuettel and Brendan Knapp.
For everything pertaining to fast_float, Daniel Lemire (and contributors).