[R] extracting values from txt with regular expression

[emorway]

Thanks for your suggestions.  Bert, in your response you raised my awareness
to "regular expressions".  Are regular expressions the same across various
languages?  Consider the following line of text:

txt_line<-" PERCENT DISCREPANCY =           0.01     PERCENT DISCREPANCY =         
-0.05"

It seems python uses the following line of code to extract the two values in
"txt_line" and store them in a variable called "v":

v = re.findall("[+-]? *(?:\d+(?:\.\d*)|\.\d+)(?:[eE][+-]?\d+)?", line)
#v[0]  0.01
#v[1]  -0.05

I tried something similar in R (but it didn't work) by using the same
regular expression, but got an error:

edm<-grep("[+-]? *(?:\d+(?:\.\d*)|\.\d+)(?:[eE][+-]?\d+)?",txt_line)
#Error: '\d' is an unrecognized escape in character string starting "[+-]?
*(?:\d"

I'm not even sure which function in R most efficiently extracts the values
from "txt_line".  Basically, I want to peel out the values and think I can
use the decimal point to construct the regular expression, but don't know
where to go from here?


--
View this message in context: http://r.789695.n4.nabble.com/extracting-values-from-txt-file-that-follow-user-supplied-quote-tp4632558p4632724.html
Sent from the R help mailing list archive at Nabble.com.