R help - Nov 2012 - select different variables from a list of data frames

Hi:
How do I select different variables from a list of data frames.
I have a list of 13 that looks like below.  Each data frame has more variables
than I need.  How do I go through the list and select the variables that I need.
In the example below, I need to get the variables "a", and
"q10" and "q14" to be returned to two separate data frames.
Thank you.
Yours, Simon Kiss

#####Sample data
  mylist<-list(df1=data.frame(a=seq(1,10,1), c=seq(1,109,1),
q10=rep('favour', 10)), df2=data.frame(a=seq(1,10,1), b=seq(15,24,1),
q14=rep('favour', 10)))

#The variables with different names that I need are
q<-c('q10', 'q14')
#My current code

dat<-mapply(function(x,y) {
  data.frame(a=x$a, y$q)
}, x=mylist, y=q)

Hi Arun:
Exactly. That's exactly what I'm looking for!
On 2012-11-12, at 5:55 PM, arun kirshna [via R] wrote:
> Hi, 
> Seems like there was a typo in "mylist" 
> mylist<-list(df1=data.frame(a=seq(1,10,1), c=seq(1,10,1),
q10=rep('favour', 10)), df2=data.frame(a=seq(1,10,1), b=seq(15,24,1),
q14=rep('favour', 10)))
> Are you looking for something like this? 
>  lapply(mylist,function(x) x[colnames(x)%in%
c("a","q10","q14")])
> #$df1 
>   #  a    q10 
> #1   1 favour 
> #2   2 favour 
> #3   3 favour 
> #4   4 favour 
> #5   5 favour 
> #6   6 favour 
> #7   7 favour 
> #8   8 favour 
> #9   9 favour 
> #10 10 favour 
> 
> #$df2 
>   #  a    q14 
> #1   1 favour 
> #2   2 favour 
> #3   3 favour 
> #4   4 favour 
> #5   5 favour 
> #6   6 favour 
> #7   7 favour 
> #8   8 favour 
> #9   9 favour 
> #10 10 favour 
> A.K. 
> 
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Simon J. Kiss, PhD
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Cell: +1 905 746 7606

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Hello,

Try the following.

lapply(mylist, function(x) x[,grep("a|q", names(x))])

Hope this helps,

Rui Barradas
Em 12-11-2012 22:34, Simon Kiss escreveu:
> Hi:
> How do I select different variables from a list of data frames.
> I have a list of 13 that looks like below.  Each data frame has more
variables than I need.  How do I go through the list and select the variables
that I need.
> In the example below, I need to get the variables "a", and
"q10" and "q14" to be returned to two separate data frames.
> Thank you.
> Yours, Simon Kiss
>
> #####Sample data
>    mylist<-list(df1=data.frame(a=seq(1,10,1), c=seq(1,109,1),
q10=rep('favour', 10)), df2=data.frame(a=seq(1,10,1), b=seq(15,24,1),
q14=rep('favour', 10)))
>
> #The variables with different names that I need are
> q<-c('q10', 'q14')
> #My current code
>
> dat<-mapply(function(x,y) {
>    data.frame(a=x$a, y$q)
> }, x=mylist, y=q)
>
> ______________________________________________
> 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,
In addition to:
mylist<-list(df1=data.frame(a=seq(1,10,1), c=seq(1,10,1),
q10=rep('favour', 10)), df2=data.frame(a=seq(1,10,1), b=seq(15,24,1),
q14=rep('favour', 10)))
lapply(mylist,function(x) x[colnames(x)%in%
c("a","q10","q14")])

you could also use:?lapply(seq_along(mylist),function(i)
mylist[[i]][names(mylist[[i]])%in%
c("a","q10","q14")])
#[[1]]
#??? a??? q10
#1?? 1 favour
#2?? 2 favour
#3?? 3 favour
#4?? 4 favour
#5?? 5 favour
#6?? 6 favour
#7?? 7 favour
#8?? 8 favour
#9?? 9 favour
#10 10 favour

#[[2]]
?# ? a??? q14
#1?? 1 favour
#2?? 2 favour
#3?? 3 favour
#4?? 4 favour
#5?? 5 favour
#6?? 6 favour
#7?? 7 favour
#8?? 8 favour
#9?? 9 favour
#10 10 favour
A.K.




----- Original Message -----
From: Simon Kiss <sjkiss at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Monday, November 12, 2012 5:34 PM
Subject: [R] select different variables from a list of data frames

Hi:
How do I select different variables from a list of data frames.
I have a list of 13 that looks like below.? Each data frame has more variables
than I need.? How do I go through the list and select the variables that I need.
In the example below, I need to get the variables "a", and
"q10" and "q14" to be returned to two separate data frames.
Thank you.
Yours, Simon Kiss

#####Sample data
? mylist<-list(df1=data.frame(a=seq(1,10,1), c=seq(1,109,1),
q10=rep('favour', 10)), df2=data.frame(a=seq(1,10,1), b=seq(15,24,1),
q14=rep('favour', 10)))

#The variables with different names that I need are
q<-c('q10', 'q14')
#My current code

dat<-mapply(function(x,y) {
? data.frame(a=x$a, y$q)
}, x=mylist, y=q)

______________________________________________
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.