[R] Referencing a column using a function argument

[Eik Vettorazzi]

Hi,
use tableName[["columnName"]] without quotes, e.g.

tableName[[columnName]] # see ?"[["

and indexing is done via
x<-length(tableName[[columnName]][tableName[[columnName]] > 6] )

but you may consider

x<-sum(tableName[[columnName]]>6)

which saves some time and typing

Hth.

Am 27.07.2011 17:22, schrieb Lin, YunHui:
> Hi all,
> 
> I've been having trouble with something that seems like it should be
> fairly straight forward. Any help at all from more experienced users is
> appreciated!
> 
>  
> 
> I'd like to write a function that uses a column name as an argument.
> However, I run into problems when I try to reference this column within
> the function.
> 
> For example,
> 
>  
> 
> findCutoff <- function(tableName, columnName) {
> 
>  
> 
>                 temporaryTable <- subset(tableName, select = c(V1, V4,
> columnName))
> 
>  
> 
>                 x <- length(tableName$columnName [tableName$columnName >
> 6] )
> 
>  
> 
>                 ...etc.
> 
> }
> 
>  
> 
> I know a couple of ways to reference a column: 
> 
> 1.       tableName$columnName
> 
> 2.       tableName[["columnName"]]
> 
> I tried turning the function arguments into a string like
> "tableName$columnName" to use within my function, but unfortunately that
> didn't work. With the second method I run into problems if I want to
> compute something like x in the example function above.
> 
>  
> 
> Any ideas, suggestions to try?
> 
>  
> 
> Thanks in advance for any responses!
> 
>  
> 
> YunHui Lisa Lin
> Intern, Customer Intelligence & Web Analytics
> 
> Moody's Corporation
> yunhui.lin at moodys.com <mailto:heather.andrews at moodys.com>  
> 
>  
> 
> 
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-- 
Eik Vettorazzi
Institut für Medizinische Biometrie und Epidemiologie
Universitätsklinikum Hamburg-Eppendorf

Martinistr. 52
20246 Hamburg

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