UNIX grep selects out lines in a file and R grep similarly selects out components of a vector of strings. On the other hand re.findall extracts substrings from strings. These are different concepts so there is no logical reason to expect that these two sets of commands behave the same. Instead, try this:
> library(gsubfn) > text <- "=832,1*R[1]K[1]*R[2]K[1]*25%" > pat <- "[^[[]([0-9]+[,.%]?[0-9]*)[^]]?" > strapply(text, pat, c)[[1]] [1] "832,1" "25%" On Fri, Apr 30, 2010 at 11:59 AM, Albert-Jan Roskam <fo...@yahoo.com> wrote: > Hi, > > The regular expression (grep) below does not behave at all like the > equivalent in Python. Also, I would be happy if somebody could tell me what > the R equivalent for Python's re.findall is. The regex filters out any > numbers not enclosed by square brackets, including fractions (with either > comma or dot as the separator) and percentages. How should the R code below > be modified so it does the same as the Python code? > > # python code >>>> import re >>>> pattern = "[^[[]([0-9]+[,.%]?[0-9]*)[^]]?" >>>> formula = "=832.1*R[1]K[1]*R[2]K[1]*25%" >>>> re.findall(pattern, formula) > ['832.1', '25%'] > > # partial R code >> formula <- "=832,1*R[1]K[1]*R[2]K[1]*25%" >> pattern <- "[^[[]([0-9]+[,.%]?[0-9]*)[^]]?" >> grep(pattern, formula, value=TRUE, perl=TRUE) > [1] "=832,1*R[1]K[1]*R[2]K[1]*25%" > > Thank you, and have a good weekend! > > Cheers!! > > Albert-Jan > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > All right, but apart from the sanitation, the medicine, education, wine, > public order, irrigation, roads, a fresh water system, and public health, > what have the Romans ever done for us? > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
