R help - Feb 2011 - recode according to specific sequence of characters within a string variable

Dear R-List, 

I have a dataframe with one column "name.of.report" containing
character values, e.g.

>df$name.of.report
"jeff_2001_teamx"
"teamy_jeff_2002"
"robert_2002_teamz"
"mary_2002_teamz"
"2003_mary_teamy"
...
(i.e. the bit of interest is not always at same position)

Now I want to recode the column "name.of.report" into the variables
"person", "year","team", like this
>new.df
"person"  "year"  "team"
jeff           2001      x
jeff           2002      y
robert       2002      z
mary        2002      z

I tried with grep()

df$person<-grep("jeff",df$name.of.report)

but of course it didn't exactly result in what I wanted to do. Could not
find any solution via RSeek. Excuse me if it is a very silly question, but can
anyone help me find a way out of this?

Thanks a lot

Alain




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On Feb 4, 2011, at 6:32 AM, D. Alain wrote:
> Dear R-List, 
> 
> I have a dataframe with one column "name.of.report" containing
character values, e.g.
> 
> 
>> df$name.of.report
> 
> "jeff_2001_teamx"
> "teamy_jeff_2002"
> "robert_2002_teamz"
> "mary_2002_teamz"
> "2003_mary_teamy"
> ...
> (i.e. the bit of interest is not always at same position)
> 
> Now I want to recode the column "name.of.report" into the
variables "person", "year","team", like this
> 
>> new.df
> 
> "person"  "year"  "team"
> jeff           2001      x
> jeff           2002      y
> robert       2002      z
> mary        2002      z
> 
> I tried with grep()
> 
> df$person<-grep("jeff",df$name.of.report)
> 
> but of course it didn't exactly result in what I wanted to do. Could
not find any solution via RSeek. Excuse me if it is a very silly question, but
can anyone help me find a way out of this?
> 
> Thanks a lot
> 
> Alain

There will be several approaches, all largely involving the use of ?regex. Here
is one:


DF <- data.frame(name.of.report = c("jeff_2001_teamx",
"teamy_jeff_2002",
                                    "robert_2002_teamz",
"mary_2002_teamz",
                                    "2003_mary_teamy"))
> DF
     name.of.report
1   jeff_2001_teamx
2   teamy_jeff_2002
3 robert_2002_teamz
4   mary_2002_teamz
5   2003_mary_teamy


DF.new <- data.frame(person = gsub("[_0-9]|team.", "",
DF$name.of.report),
                     year = gsub(".*([0-9]{4}).*","\\1",
DF$name.of.report),
                     team = gsub(".*team(.).*","\\1",
DF$name.of.report))

> DF.new
  person year team
1   jeff 2001    x
2   jeff 2002    y
3 robert 2002    z
4   mary 2002    z
5   mary 2003    y



HTH,

Marc Schwartz

You can do this with regular expressions, since you want to extract specific
values from the string I would suggest learning about the gsubfn package, it is
a bit easier with gsubfn than with the other matching tools.


-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of D. Alain
> Sent: Friday, February 04, 2011 5:33 AM
> To: r-help at r-project.org
> Subject: [R] recode according to specific sequence of characters within
> a string variable
> 
> Dear R-List,
> 
> I have a dataframe with one column "name.of.report" containing
> character values, e.g.
> 
> 
> >df$name.of.report
> 
> "jeff_2001_teamx"
> "teamy_jeff_2002"
> "robert_2002_teamz"
> "mary_2002_teamz"
> "2003_mary_teamy"
> ...
> (i.e. the bit of interest is not always at same position)
> 
> Now I want to recode the column "name.of.report" into the
variables
> "person", "year","team", like this
> 
> >new.df
> 
> "person"? "year"? "team"
> jeff?????????? 2001????? x
> jeff?????????? 2002????? y
> robert?????? 2002????? z
> mary??????? 2002????? z
> 
> I tried with grep()
> 
> df$person<-grep("jeff",df$name.of.report)
> 
> but of course it didn't exactly result in what I wanted to do. Could
> not find any solution via RSeek. Excuse me if it is a very silly
> question, but can anyone help me find a way out of this?
> 
> Thanks a lot
> 
> Alain
> 
> 
> 
> 
> 	[[alternative HTML version deleted]]