[R] Write a function that allows access to columns of a passed dataframe.

[Rui Barradas]

Hello,

For some reason I got moderation in reply to Bert's post so I'll retry.
Get rid of 'xx', keep 'yy':

frame[, yy]  # this works

Hope this helps,

Rui Barradas

Em 05-12-2016 15:29, John Sorkin escreveu:
> Rui,
> I appreciate your suggestion, but eliminating the deparse statement does
> not solve my problem. Do you have any other suggestions? See code below.
> Thank you,
> John
>
> mydf <-
> data.frame(id=c(1,2,3,4,5),sex=c("M","M","M","F","F"),age=c(20,34,43,32,21))
> mydf
> class(mydf)
>
> myfun <- function(frame,var){
>    call <- match.call()
>    print(call)
>
>    indx <- match(c("frame","var"),names(call),nomatch=0)
>    print(indx)
>    if(indx[1]==0) stop("Function called without sufficient arguments!")
>
>    cat("I can get the name of the dataframe as a text string!\n")
>    #xx <- deparse(substitute(frame))
>    print(xx)
>
>    cat("I can get the name of the column as a text string!\n")
>    #yy <- deparse(substitute(var))
>    print(yy)
>
>    # This does not work.
>    print(frame[,var])
>
>    # This does not work.
>    print(frame[,"var"])
>
>
>    # This does not work.
>    col <- xx[,"yy"]
>
>    # Nor does this work.
>    col <- xx[,yy]
>    print(col)
> }
>
> myfun(mydf,age)
>
>
> myfun()
>
>
>
>
>
>
>
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and
> Geriatric Medicine
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
>  >>> Rui Barradas <ruipbarradas at sapo.pt> 12/05/16 10:17 AM >>>
> Hello,
>
> You don't need xx <- deparse(substitute(...)), since you are passing the
> data.frame to your function. Just use
>
>
> myfun <- function(frame,var){
>
> [...]
>
> # Nor does this work.
> col <- frame[,yy]
> print(col)
> }
>
> myfun(mydf,age)
> myfun(frame = mydf, var = age)
> [1] 2 3
> I can get the name of the dataframe as a text string!
> [1] "mydf"
> I can get the name of the column as a text string!
> [1] "age"
> [1] 20 34 43 32 21
>
>
> Hope this helps,
>
> Rui Barradas
>
>
>
> Em 05-12-2016 14:44, John Sorkin escreveu:
>  > I am trying to write a function which, when passed the name of a
> dataframe and the name of a column of the dataframe, will allow me to
> work on the columns of a dataframe. I can not get my code to work.
> Please see the code below. Any help in getting the function to work
> would be appreciated.
>  >
>  >
>  >
>  >
>  > mydf <-
> data.frame(id=c(1,2,3,4,5),sex=c("M","M","M","F","F"),age=c(20,34,43,32,21))
>  > mydf
>  > class(mydf)
>  >
>  >
>  > myfun <- function(frame,var){
>  > call <- match.call()
>  > print(call)
>  >
>  >
>  > indx <- match(c("frame","var"),names(call),nomatch=0)
>  > print(indx)
>  > if(indx[1]==0) stop("Function called without sufficient arguments!")
>  >
>  >
>  > cat("I can get the name of the dataframe as a text string!\n")
>  > xx <- deparse(substitute(frame))
>  > print(xx)
>  >
>  >
>  > cat("I can get the name of the column as a text string!\n")
>  > yy <- deparse(substitute(var))
>  > print(yy)
>  >
>  >
>  > # This does not work.
>  > col <- xx[,"yy"]
>  >
>  >
>  > # Nor does this work.
>  > col <- xx[,yy]
>  > print(col)
>  > }
>  >
>  >
>  > myfun(mydf,age)
>  >
>  > John David Sorkin M.D., Ph.D.
>  > Professor of Medicine
>  > Chief, Biostatistics and Informatics
>  > University of Maryland School of Medicine Division of Gerontology and
> Geriatric Medicine
>  > Baltimore VA Medical Center
>  > 10 North Greene Street
>  > GRECC (BT/18/GR)
>  > Baltimore, MD 21201-1524
>  > (Phone) 410-605-7119
>  > (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>  >
>  >
>  >
>  >
>  > John David Sorkin M.D., Ph.D.
>  > Professor of Medicine
>  > Chief, Biostatistics and Informatics
>  > University of Maryland School of Medicine Division of Gerontology and
> Geriatric Medicine
>  > Baltimore VA Medical Center
>  > 10 North Greene Street
>  > GRECC (BT/18/GR)
>  > Baltimore, MD 21201-1524
>  > (Phone) 410-605-7119
>  > (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>  >
>  >
>  >
>  >
>  >
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