R help - Feb 2010 - How to add a variable to a dataframe whose values are conditional upon the values of an existing variable

Hi everyone,

I am at my wits end with what I believe would be considered simple by a more
experienced R user. I want to know how to add a variable to a dataframe whose
values?are conditional?on the values of an existing?variable.?I can't seem
to make an ifelse statement work?for my situation.?The existing variable?in my
dataframe is?a character variable named DOW which contains abbreviated day names
(SAT, SUN, MON.....FRI). I want to add a numerical variable named DOW1 to my
dataframe that will?take?on the value?1 if DOW equals "SAT", 2 if DOW
equals "SUN", 3 if DOW equals "MON",.....,7 if DOW equals
"FRI".
I? know this must be a simple problem but I have searched everywhere and tried
everything I could think of. Any help would be greatly appreciated.

Thank you,

Mike

You mention ifelse, so for completeness, I will show you a solution that 
should work with that.  There are other plenty of other possibilities 
though, I am sure.  The follow is not tested..

Assume 'my.df' is your data.frame, containing a variable
"DOW".

my.df$DOW1 <- ifelse(my.df$DOW == "SAT", 1,
                      ifelse(my.df$DOW == "SUN", 2,
                         ifelse(my.df$DOW == "MON", 3,
                           ifelse(my.df$DOW == "TUE", 4,
                              ifelse(my.df$DOW == "WED", 5,
                                 ifelse(my.df$DOW == "THU", 6,
                                      7))))))

(don't know if the number of closing ")" is right, but you get the
idea...

Erik


Steve Matco wrote:
> Hi everyone,
> 
> I am at my wits end with what I believe would be considered simple by a
more experienced R user. I want to know how to add a variable to a dataframe
whose values are conditional on the values of an existing variable. I can't
seem to make an ifelse statement work for my situation. The existing variable in
my dataframe is a character variable named DOW which contains abbreviated day
names (SAT, SUN, MON.....FRI). I want to add a numerical variable named DOW1 to
my dataframe that will take on the value 1 if DOW equals "SAT", 2 if
DOW equals "SUN", 3 if DOW equals "MON",.....,7 if DOW
equals "FRI".
> I  know this must be a simple problem but I have searched everywhere and
tried everything I could think of. Any help would be greatly appreciated.
> 
> Thank you,
> 
> Mike
> 
> 
> 
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Try this:

sapply(c('SAT', 'SUN', 'MON', 'FRI'), switch,
SAT = 1, SUN = 2, MON 3, FRI = 4)


On Fri, Feb 26, 2010 at 4:31 PM, Steve Matco <h20strider at yahoo.com>
wrote:
> Hi everyone,
>
> I am at my wits end with what I believe would be considered simple by a
more experienced R user. I want to know how to add a variable to a dataframe
whose values?are conditional?on the values of an existing?variable.?I can't
seem to make an ifelse statement work?for my situation.?The existing variable?in
my dataframe is?a character variable named DOW which contains abbreviated day
names (SAT, SUN, MON.....FRI). I want to add a numerical variable named DOW1 to
my dataframe that will?take?on the value?1 if DOW equals "SAT", 2 if
DOW equals "SUN", 3 if DOW equals "MON",.....,7 if DOW
equals "FRI".
> I? know this must be a simple problem but I have searched everywhere and
tried everything I could think of. Any help would be greatly appreciated.
>
> Thank you,
>
> Mike
>
>
>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

You could also try a series of simple ifelse statements.  I just tried  
the following and got it to work, though I am sure there is a faster  
way.

  t=c("cow", "dog", "chick")
  y=c(1,3,4)
mat=cbind(t,y)
mat=as.data.frame(mat)

 > mat
       t y
1   cow 1
2   dog 3
3 chick 4

mat$g=ifelse(mat$t=="cow", 1, 6)
mat$g=ifelse(mat$t=="dog", 2, mat$g)
mat$g=ifelse(mat$t=="chick", 3, mat$g)

 > mat
       t y g
1   cow 1 1
2   dog 3 2
3 chick 4 3

To days of the week would only be 7 statements.

Andrew Miles
Department of Sociology
Duke University

On Feb 26, 2010, at 2:31 PM, Steve Matco wrote:
> Hi everyone,
>
> I am at my wits end with what I believe would be considered simple  
> by a more experienced R user. I want to know how to add a variable  
> to a dataframe whose values are conditional on the values of an  
> existing variable. I can't seem to make an ifelse statement work for  
> my situation. The existing variable in my dataframe is a character  
> variable named DOW which contains abbreviated day names (SAT, SUN,  
> MON.....FRI). I want to add a numerical variable named DOW1 to my  
> dataframe that will take on the value 1 if DOW equals "SAT", 2 if
> DOW equals "SUN", 3 if DOW equals "MON",.....,7 if DOW
equals "FRI".
> I  know this must be a simple problem but I have searched everywhere  
> and tried everything I could think of. Any help would be greatly  
> appreciated.
>
> Thank you,
>
> Mike
>
>
>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Hi, two approaches at least.

a. a nested ifelse statement
b. merging the original data frame with DOW in it with a data frame that
holds the day "MON" to "SUN" and their indicators.

Both approaches illustrated below:

DOW=rep(c("MON","TUE"),100)

#nested ifelse approach
DOW.ind=ifelse(DOW=="MON",1,ifelse(DOW=="TUE",2,0)) 
#continue to nest ifelse statements for more days

DOW.ind

#merging approach
day=c("MON","TUE") 
ind=c(1,2)
ind.frame=data.frame(day,ind)
merge(data.frame(DOW),ind.frame,by.x="DOW",by.y="day",all.x=T,all.y=F)

HTH,
Daniel

-------------------------
cuncta stricte discussurus
-------------------------
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Steve Matco
Sent: Friday, February 26, 2010 2:32 PM
To: r-help at r-project.org
Subject: [R] How to add a variable to a dataframe whose values are
conditional upon the values of an existing variable

Hi everyone,

I am at my wits end with what I believe would be considered simple by a more
experienced R user. I want to know how to add a variable to a dataframe
whose values?are conditional?on the values of an existing?variable.?I can't
seem to make an ifelse statement work?for my situation.?The existing
variable?in my dataframe is?a character variable named DOW which contains
abbreviated day names (SAT, SUN, MON.....FRI). I want to add a numerical
variable named DOW1 to my dataframe that will?take?on the value?1 if DOW
equals "SAT", 2 if DOW equals "SUN", 3 if DOW equals
"MON",.....,7 if DOW
equals "FRI". 
I? know this must be a simple problem but I have searched everywhere and
tried everything I could think of. Any help would be greatly appreciated.

Thank you,

Mike




______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

You can work with factor also:

week <- c('SAT', 'SUN', 'MON', 'FRI')
factor(week, levels = week, labels = 1:4)

On Fri, Feb 26, 2010 at 4:31 PM, Steve Matco <h20strider at yahoo.com>
wrote:
> Hi everyone,
>
> I am at my wits end with what I believe would be considered simple by a
more experienced R user. I want to know how to add a variable to a dataframe
whose values?are conditional?on the values of an existing?variable.?I can't
seem to make an ifelse statement work?for my situation.?The existing variable?in
my dataframe is?a character variable named DOW which contains abbreviated day
names (SAT, SUN, MON.....FRI). I want to add a numerical variable named DOW1 to
my dataframe that will?take?on the value?1 if DOW equals "SAT", 2 if
DOW equals "SUN", 3 if DOW equals "MON",.....,7 if DOW
equals "FRI".
> I? know this must be a simple problem but I have searched everywhere and
tried everything I could think of. Any help would be greatly appreciated.
>
> Thank you,
>
> Mike
>
>
>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

Here is another approach (I think this is the simplest):

daylkp <- c(SAT=1, SUN=2, MON=3, TUE=4, WED=5, THU=6, FRI=7)

tmp.in <- sample( names(daylkp), 25, TRUE )
tmp.out <- daylkp[tmp.in]

names(tmp.out) <- NULL # optional


hope this helps,

-- 
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 Steve Matco
> Sent: Friday, February 26, 2010 12:32 PM
> To: r-help at r-project.org
> Subject: [R] How to add a variable to a dataframe whose values are
> conditional upon the values of an existing variable
> 
> Hi everyone,
> 
> I am at my wits end with what I believe would be considered simple by a
> more experienced R user. I want to know how to add a variable to a
> dataframe whose values?are conditional?on the values of an
> existing?variable.?I can't seem to make an ifelse statement work?for my
> situation.?The existing variable?in my dataframe is?a character
> variable named DOW which contains abbreviated day names (SAT, SUN,
> MON.....FRI). I want to add a numerical variable named DOW1 to my
> dataframe that will?take?on the value?1 if DOW equals "SAT", 2 if
DOW
> equals "SUN", 3 if DOW equals "MON",.....,7 if DOW
equals "FRI".
> I? know this must be a simple problem but I have searched everywhere
> and tried everything I could think of. Any help would be greatly
> appreciated.
> 
> Thank you,
> 
> Mike
> 
> 
> 
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

there's a recode function in the Hmisc package, but it's difficult (at
least
for me) to find documentation for it

library(Hmisc)
week <- c('SAT', 'SUN', 'MON', 'FRI');
recode(week,c('SAT', 'SUN', 'MON', 'FRI'),1:4)

HTH
-- 
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