[R] Listing Variables

From: Farrel Buchinsky <fjbuch_at_gmail.com>
Date: Thu 04 May 2006 - 00:46:25 EST

How does one create a vector whose contents is the list of variables in a dataframe pertaining to a particular pattern? This is so simple but I cannot find a straightforward answer. I want to be able to pass the contents of that list to a "for" loop.

So let us assume that one has a dataframe whose name is Data. And let us assume one had the height of a group of people measured at various ages.

It could be made up of vectors Data$PersonalID, Data$FirstName, Data$LastName, Data$Height.1, Data$Height.5, Data$Height.9, Data$Height.10,Data$Height.12,Data$Height.20....many many more variables.

How would one create a vector of all the Height variable names.

The simple workaround is to not bother creating the vector "Data$Height.1"
"Data$Height.5" "Data$Height.9" "Data$Height.10"
"Data$Height.12""Data$Height.20"...but rather just to use the sapply
function. However with some functions the sapply will not work and it is necessary to supply each variable name to a function (see thread at Repeating tdt function on thousands of variables)

This is such a core capability. I would like to see it in the R-Wiki but could not find it there.

Farrel Buchinsky, MD
Pediatric Otolaryngologist
Allegheny General Hospital
Pittsburgh, PA

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Received on Thu May 04 01:00:23 2006

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