I have a vector of strings that contain mathematical expressions. E.g.,
x <- c("5 <= 7", "z = 1+2")
and I would like to decompose each expression into its left- and
right-hand-side components etc., output something like
"5" "<=" "7"
"z" "=" "1" "+" "2"
Is there something built into the R language to accomplish this?
Thanks for advance.
Dan
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If your syntax is like R's syntax then parse() can help. R> p <- parse(text="z = 1 + 2") R> p[[1]] # the first (& only) expression in "z = 1 + 2" z = 1 + 2 R> as.list(p[[1]]) # the 'function' called (`=`) and its 'arguments' [[1]] `=` [[2]] z [[3]] 1 + 2 R> as.list(p[[1]][[3]]) # ditto for the 2nd argument above [[1]] `+` [[2]] [1] 1 [[3]] [1] 2 Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com> -----Original Message----- > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf > Of Dan Murphy > Sent: Wednesday, July 03, 2013 10:38 AM > To: R-help at r-project.org > Subject: [R] Splitting a string expression into components > > I have a vector of strings that contain mathematical expressions. E.g., > x <- c("5 <= 7", "z = 1+2") > and I would like to decompose each expression into its left- and > right-hand-side components etc., output something like > > "5" "<=" "7" > "z" "=" "1" "+" "2" > > Is there something built into the R language to accomplish this? > Thanks for advance. > Dan > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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.
strsplit(x, split= " ") 2013/7/3 Dan Murphy <chiefmurphy@gmail.com>> I have a vector of strings that contain mathematical expressions. E.g., > x <- c("5 <= 7", "z = 1+2") > and I would like to decompose each expression into its left- and > right-hand-side components etc., output something like > > "5" "<=" "7" > "z" "=" "1" "+" "2" > > Is there something built into the R language to accomplish this? > Thanks for advance. > Dan > > [[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. >-- Sincerely yours, Yulia Matveeva, Department of Statistical Modelling, Faculty of Mathematics and Mechanics, St Petersburg State University, Russia [[alternative HTML version deleted]]