R help - Oct 2010 - dataframe, transform, strsplit

Hi,

I have a dataframe that has a column of vectors that I need to extract off
the character string before the first '.' character and put it into a
separate column.  I thought I could use 'strsplit' for it within
'transform', but I can't seem to get the right invocation.  Here is
a sample
dataframe that has what I have, what I want, and what I get.  Can someone
tell me how to get what is in the 'want' column from the 'have'
column
programatically?

tia,
Matt

df <- data.frame(have=c("a.b.c", "d.e.f",
"g.h.i"), want=c("a","d","g"))
df.xform <- transform(df, get=strsplit(as.character(have),
split=".",
fixed=TRUE)[[1]][1])
df.xform

	[[alternative HTML version deleted]]

try this:
> df
   have want
1 a.b.c    a
2 d.e.f    d
3 g.h.i    g
> df$get <- gsub("^([^.]+).*", "\\1", df$have)
> df
   have want get
1 a.b.c    a   a
2 d.e.f    d   d
3 g.h.i    g   g


On Mon, Oct 25, 2010 at 12:53 PM, Matthew Pettis
<matthew.pettis at gmail.com> wrote:
> Hi,
>
> I have a dataframe that has a column of vectors that I need to extract off
> the character string before the first '.' character and put it into
a
> separate column. ?I thought I could use 'strsplit' for it within
> 'transform', but I can't seem to get the right invocation.
?Here is a sample
> dataframe that has what I have, what I want, and what I get. ?Can someone
> tell me how to get what is in the 'want' column from the
'have' column
> programatically?
>
> tia,
> Matt
>
> df <- data.frame(have=c("a.b.c", "d.e.f",
"g.h.i"), want=c("a","d","g"))
> df.xform <- transform(df, get=strsplit(as.character(have),
split=".",
> fixed=TRUE)[[1]][1])
> df.xform
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


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

What is the problem that you are trying to solve?

On Mon, Oct 25, 2010 at 12:53 PM, Matthew Pettis
<matthew.pettis at gmail.com> wrote:
> Hi,
>
> I have a dataframe that has a column of vectors that I need to extract off
> the character string before the first '.' character and put it into
a
> separate column. ?I thought I could use 'strsplit' for it within
> 'transform', but I can't seem to get the right invocation.
?Here is a sample
> dataframe that has what I have, what I want, and what I get. ?Can someone
> tell me how to get what is in the 'want' column from the
'have' column
> programatically?
>
> tia,
> Matt
>
> df <- data.frame(have=c("a.b.c", "d.e.f",
"g.h.i"), want=c("a","d","g"))
> df.xform <- transform(df, get=strsplit(as.character(have),
split=".",
> fixed=TRUE)[[1]][1])
> df.xform
>
Try replacing the dot [.] and everything thereafter .* with nothing ""
like this:

transform(df, want = sub("[.].*", "", have))

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