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Daisy Englert Duursma

2010-Oct-26 03:56 UTC

[R] divide column in a dataframe based on a character

Hello,

If I have a dataframe:

example(data.frame)
zz<-c("aa_bb","bb_cc","cc_dd","dd_ee","ee_ff","ff_gg","gg_hh","ii_jj","jj_kk","kk_ll")
ddd <- cbind(dd, group = zz)

and I want to divide the column named group by the "_", how would I do
this?

so instead of the first row being
 x   y  fac char  group
 1  1   C    a     aa_bb

it should be:
 x  y fac  char group_a    group_b
 1  1   C    a      aa             bb



I know for a vector I can:
x1 <- c("a_b","b_c","c_d")
do.call("rbind",strsplit(x1, "_"))

but I am not sure how this relates to my data.frame

Thanks,
Daisy


-- 
Daisy Englert Duursma

Room E8C156
Dept. Biological Sciences
Macquarie University? NSW? 2109
Australia

Bill.Venables at csiro.au

2010-Oct-26 04:23 UTC

head link

[R] divide column in a dataframe based on a character

You are nearly there.
____

example(data.frame)
zz <-
c("aa_bb","bb_cc","cc_dd","dd_ee","ee_ff",
	  
"ff_gg","gg_hh","ii_jj","jj_kk","kk_ll")
ddd <- cbind(dd, group = zz)

ddd <- within(ddd, {
	group <- as.character(group)
	tmp <- do.call(rbind, strsplit(group, "_"))
	group_b <- tmp[,2]
	group_a <- tmp[,1]
	rm(tmp, group)
})

____
> ddd   x  y fac char group_a group_b
1  1  1   B    a      aa      bb
2  1  2   B    b      bb      cc
3  1  3   A    c      cc      dd
4  1  4   A    d      dd      ee
5  1  5   A    e      ee      ff
6  1  6   C    f      ff      gg
7  1  7   A    g      gg      hh
8  1  8   B    h      ii      jj
9  1  9   C    i      jj      kk
10 1 10   B    j      kk      ll

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Daisy Englert Duursma
Sent: Tuesday, 26 October 2010 1:57 PM
To: r-help at r-project.org
Subject: [R] divide column in a dataframe based on a character

Hello,

If I have a dataframe:

example(data.frame)
zz<-c("aa_bb","bb_cc","cc_dd","dd_ee","ee_ff","ff_gg","gg_hh","ii_jj","jj_kk","kk_ll")
ddd <- cbind(dd, group = zz)

and I want to divide the column named group by the "_", how would I do
this?

so instead of the first row being
 x   y  fac char  group
 1  1   C    a     aa_bb

it should be:
 x  y fac  char group_a    group_b
 1  1   C    a      aa             bb



I know for a vector I can:
x1 <- c("a_b","b_c","c_d")
do.call("rbind",strsplit(x1, "_"))

but I am not sure how this relates to my data.frame

Thanks,
Daisy


-- 
Daisy Englert Duursma

Room E8C156
Dept. Biological Sciences
Macquarie University? NSW? 2109
Australia

______________________________________________
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and provide commented, minimal, self-contained, reproducible code.

David Winsemius

2010-Oct-26 04:33 UTC

head link

[R] divide column in a dataframe based on a character

On Oct 25, 2010, at 8:56 PM, Daisy Englert Duursma wrote:
> Hello,
>
> If I have a dataframe:
>
> example(data.frame)
> zz<- 
> c 
> ("aa_bb 
> ","bb_cc 
>
","cc_dd","dd_ee","ee_ff","ff_gg","gg_hh","ii_jj","jj_kk","kk_ll")
> ddd <- cbind(dd, group = zz)
>
> and I want to divide the column named group by the "_", how would
I
> do this?
>
> so instead of the first row being
> x   y  fac char  group
> 1  1   C    a     aa_bb
>
> it should be:
> x  y fac  char group_a    group_b
> 1  1   C    a      aa             bb
>
>
>
> I know for a vector I can:
> x1 <- c("a_b","b_c","c_d")
> do.call("rbind",strsplit(x1, "_"))
>
> but I am not sure how this relates to my data.frame
The group columns is a factor, as is the default structure for non- 
numeric character arguments to dataframe() and cbind.data.frame(). If  
you want to the split values you must first convert to character:

 > ddd$group_a <- lapply(strsplit(as.character(ddd$group), "_"),
"[", 1)
 > ddd$group_b <- lapply(strsplit(as.character(ddd$group), "_"),
"[", 2)
 > ddd
    x  y fac char group group_a group_b
1  1  1   C    a aa_bb    aa     bb
2  1  2   B    b bb_cc    bb     cc
3  1  3   C    c cc_dd    cc     dd
4  1  4   C    d dd_ee    dd     ee
5  1  5   B    e ee_ff    ee     ff
6  1  6   A    f ff_gg    ff     gg
7  1  7   C    g gg_hh    gg     hh
8  1  8   A    h ii_jj    ii     jj
9  1  9   B    i jj_kk    jj     kk
10 1 10   B    j kk_ll    kk     ll

-- 
David.

Daisy Englert Duursma

2010-Oct-26 04:47 UTC

head link

[R] divide column in a dataframe based on a character

Thanks for the help. Easy as..

On Tue, Oct 26, 2010 at 3:33 PM, David Winsemius <dwinsemius at
comcast.net> wrote:>
> On Oct 25, 2010, at 8:56 PM, Daisy Englert Duursma wrote:
>
>> Hello,
>>
>> If I have a dataframe:
>>
>> example(data.frame)
>>
>>
zz<-c("aa_bb","bb_cc","cc_dd","dd_ee","ee_ff","ff_gg","gg_hh","ii_jj","jj_kk","kk_ll")
>> ddd <- cbind(dd, group = zz)
>>
>> and I want to divide the column named group by the "_", how
would I do
>> this?
>>
>> so instead of the first row being
>> x ? y ?fac char ?group
>> 1 ?1 ? C ? ?a ? ? aa_bb
>>
>> it should be:
>> x ?y fac ?char group_a ? ?group_b
>> 1 ?1 ? C ? ?a ? ? ?aa ? ? ? ? ? ? bb
>>
>>
>>
>> I know for a vector I can:
>> x1 <- c("a_b","b_c","c_d")
>> do.call("rbind",strsplit(x1, "_"))
>>
>> but I am not sure how this relates to my data.frame
>
> The group columns is a factor, as is the default structure for non-numeric
> character arguments to dataframe() and cbind.data.frame(). If you want to
> the split values you must first convert to character:
>
>> ddd$group_a <- lapply(strsplit(as.character(ddd$group),
"_"), "[", 1)
>> ddd$group_b <- lapply(strsplit(as.character(ddd$group),
"_"), "[", 2)
>> ddd
> ? x ?y fac char group group_a group_b
> 1 ?1 ?1 ? C ? ?a aa_bb ? ?aa ? ? bb
> 2 ?1 ?2 ? B ? ?b bb_cc ? ?bb ? ? cc
> 3 ?1 ?3 ? C ? ?c cc_dd ? ?cc ? ? dd
> 4 ?1 ?4 ? C ? ?d dd_ee ? ?dd ? ? ee
> 5 ?1 ?5 ? B ? ?e ee_ff ? ?ee ? ? ff
> 6 ?1 ?6 ? A ? ?f ff_gg ? ?ff ? ? gg
> 7 ?1 ?7 ? C ? ?g gg_hh ? ?gg ? ? hh
> 8 ?1 ?8 ? A ? ?h ii_jj ? ?ii ? ? jj
> 9 ?1 ?9 ? B ? ?i jj_kk ? ?jj ? ? kk
> 10 1 10 ? B ? ?j kk_ll ? ?kk ? ? ll
>
> --
> David.
>
>


-- 
Daisy Englert Duursma

Room E8C156
Dept. Biological Sciences
Macquarie University? NSW? 2109
Australia

Tel +61 2 9850 9256



Unit 2, 35 Denison St
Hornsby, NSW 2077

Mobile: 0421858456

Brian Diggs

2010-Oct-26 20:39 UTC

head link

[R] divide column in a dataframe based on a character

On 10/25/2010 8:56 PM, Daisy Englert Duursma wrote:> Hello,
>
> If I have a dataframe:
>
> example(data.frame)
>
zz<-c("aa_bb","bb_cc","cc_dd","dd_ee","ee_ff","ff_gg","gg_hh","ii_jj","jj_kk","kk_ll")
> ddd<- cbind(dd, group = zz)
>
> and I want to divide the column named group by the "_", how would
I do this?
>
> so instead of the first row being
>   x   y  fac char  group
>   1  1   C    a     aa_bb
>
> it should be:
>   x  y fac  char group_a    group_b
>   1  1   C    a      aa             bb
>
>
>
> I know for a vector I can:
> x1<- c("a_b","b_c","c_d")
> do.call("rbind",strsplit(x1, "_"))
>
> but I am not sure how this relates to my data.frame
>
> Thanks,
> Daisy
Daisy,

You've already gotten a couple of responses, but I thought I'd point out
an different approach (the let-someone-else-deal-with-the-details 
approach).  The reshape package has a colsplit function which is 
designed just for this sort of thing.

library("reshape")

ddd <- cbind(ddd, colsplit(ddd$group, split="_",
names=c("group_a",
"group_b")))

-- 
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University

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