[R] gsub,regex and replacing

[arnaud Gaboury]

Sorry Jim, here is my data.frame:

avprix <-
structure(list(DESCRIPTION = c("CORN Jul/10", "CORN May/10", 
"ROBUSTA COFFEE (10) Jul/10", "SOYBEANS Jul/10", "SPCL HIGH GRADE ZINC USD
Jul/10", 
"STANDARD LEAD USD Jul/10"), prix = c(-1.5, -1082, 11084, 1983.5, 
-2464, -118), quantity = c(0, -3, 8, 2, -1, 0)), .Names = c("DESCRIPTION", 
"prix", "quantity"), row.names = c(NA, -6L), class = "data.frame")




From: jim holtman [mailto:jholtman at gmail.com] 
Sent: Wednesday, April 28, 2010 1:31 PM
To: arnaud Gaboury
Cc: r-help at r-project.org
Subject: Re: [R] gsub,regex and replacing

Next time you include a data frame that has spaces in the fields, please
consider using 'dput' to provided the data.  It is hard to read in
otherwise.
 
Will this do it:
 
> x <- read.table(textConnection("                     DESCRIPTION    prix
quantity
+ 1                     'CORN Jul/10'    -1.5        0
+ 2                     'CORN May/10' -1082.0       -3
+ 3      'ROBUSTA COFFEE (10) Jul/10' 11084.0        8
+ 4                 'SOYBEANS Jul/10'  1983.5        2
+ 5 'SPCL HIGH GRADE ZINC USD Jul/10' -2464.0       -1
+ 6        'STANDARD LEAD USD Aug/10'  -118.0        0"), header=TRUE,
as.is=TRUE)
.> 
> x$DESCRIPTION <- sub("USD [[:alpha:]]+/[[:digit:]]+", "USD",
x$DESCRIPTION)
> 
> x
                 DESCRIPTION    prix quantity
1                CORN Jul/10    -1.5        0
2                CORN May/10 -1082.0       -3
3 ROBUSTA COFFEE (10) Jul/10 11084.0        8
4            SOYBEANS Jul/10  1983.5        2
5   SPCL HIGH GRADE ZINC USD -2464.0       -1
6          STANDARD LEAD USD  -118.0        0

On Wed, Apr 28, 2010 at 7:13 AM, arnaud Gaboury <arnaud.gaboury at gmail.com>
wrote:
Dear group,

I need to modify some characters in a data frame. I want to use gsub and the
regex functionalities to do this.

Here is the data frame (df):

                     DESCRIPTION    prix quantity
1                     CORN Jul/10    -1.5        0
2                     CORN May/10 -1082.0       -3
3      ROBUSTA COFFEE (10) Jul/10 11084.0        8
4                 SOYBEANS Jul/10  1983.5        2
5 SPCL HIGH GRADE ZINC USD Jul/10 -2464.0       -1
6        STANDARD LEAD USD Aug/10  -118.0        0


For each df$DESCRIPTION element containing "USD" I want to remove the last
part of it(i.e Jul/10, or Aug/10...).
I was thinking of something like that:

>Df$DESCRIPTION<-gsub("USD","new name whithout last part",df$DESCRIPTION)

to get this following result:


                     DESCRIPTION    prix quantity
1                     CORN Jul/10    -1.5        0
2                     CORN May/10 -1082.0       -3
3      ROBUSTA COFFEE (10) Jul/10 11084.0        8
4                 SOYBEANS Jul/10  1983.5        2
5        SPCL HIGH GRADE ZINC USD -2464.0       -1
6               STANDARD LEAD USD  -118.0        0

My problem is that I have no idea how to write the regular expression in my
command line.

Any help would be appreciated.

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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?