[R] Applying variable labels across a data frame

[Gabriel Baud-Bovy]

You get a list, not a data.frame. Try,

as.data.frame(lapply( myQFvars, myLabeler ))

Gabriel

At 05:10 PM 12/18/2006, Muenchen, Robert A (Bob) wrote:
>Hi All,
>
>I'm working on a class example that demonstrates one way to deal with
>factors and their labels. I create a function called myLabeler and apply
>it with lapply. It works on the whole data frame when I subscript it as
>in lapply( myQFvars[ ,myQFnames ], myLabeler ) but does not work if I
>leave the [] subscripts off. I would appreciate it if anyone could tell
>me why. The program below works up until the final two statements.
>
>Thanks,
>Bob
>
>
># Assigning factor labels to potentially lots of vars.
>
>mystring<-
>("id,workshop,gender,q1,q2,q3,q4
>  1,1,f,1,1,5,1
>  2,2,f,2,1,4,1
>  3,1,f,2,2,4,3
>  4,2,f,3,1, ,3
>  5,1,m,4,5,2,4
>  6,2,m,5,4,5,5
>  7,1,m,5,3,4,4
>  8,2,m,4,5,5,9")
>
>mydata<-read.table(textConnection(mystring),
>    header=TRUE,sep=",",row.names="id",na.strings="9")
>print(mydata)
>
># Create copies of q variables to use as factors
># so we can count them.
>myQlevels <- c(1,2,3,4,5)
>myQlabels <- c("Strongly Disagree",
>                "Disagree",
>                "Neutral",
>                "Agree",
>                "Strongly Agree")
>print(myQlevels)
>print(myQlabels)
>
># Generate two sets of var names to use.
>myQnames  <-   paste( "q",  1:4, sep="")
>myQFnames <- paste( "qf", 1:4, sep="")
>print(myQnames) #The original names.
>print(myQFnames)  #The names for new factor variables.
>
># Extract the q variables to a separate data frame.
>myQFvars <- mydata[ ,myQnames]
>print(myQFvars)
>
># Rename all the variables with F for Factor.
>colnames(myQFvars) <- myQFnames
>print(myQFvars)
>
># Create a function to apply the labels to lots of variables.
>myLabeler <- function(x) { factor(x, myQlevels, myQlabels) }
>
># Here's how to use the function on one variable.
>summary( myLabeler(myQFvars["qf1"]) )
>
>#Apply it to all the variables. This method works.
>myQFvars[ ,myQFnames] <- lapply( myQFvars[ ,myQFnames ], myLabeler )
>summary(myQFvars) #Here are the results I wanted.
>
># This is the same as above but using the unsubscripted
># data frame name. It does not work.
>myTest <- lapply( myQFvars, myLabeler )
>summary(myTest) #I'm not sure what these results are.
>
>=========================================================
>   Bob Muenchen (pronounced Min'-chen), Manager
>   Statistical Consulting Center
>   U of TN Office of Information Technology
>   200 Stokely Management Center, Knoxville, TN 37996-0520
>   Voice: (865) 974-5230
>   FAX:   (865) 974-4810
>   Email: muenchen at utk.edu
>   Web:   http://oit.utk.edu/scc,
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>
>______________________________________________
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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.

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