[R] select different variables from a list of data frames

[arun]

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)

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