[R] [plyr] Question regarding ddply: use of .(as.name(varname)) and varname in ddply function

[Peter Ehlers]

On 2010-12-06 01:58, Sunny Srivastava wrote:
> Dear R-Helpers:
>
> I am using trying to use *ddply* to extract min and max of a particular
> column in a data.frame. I am using two different forms of the function:
>
>
> ## var_name_to_split is a string -- something like "var1" which is the name
> of a column in data.frame
>
> ddply( df, .(as.name(var_name_to_split)), function(x) c(min(x[ , 3] , max(x[
> , 3]))) ## fails with an error - case 1
> ddply( df, var_name_to_split , function(x) c(min(x[ , 3] , max(x[ , 3])))
>                 ## works fine - case 2
>

Try it without the .(), i.e. ddply(df, as.name(), ....)

Peter Ehlers

> I can't understand why I get the error in case 1. Can someone help me
> please?
>
> Thank you in advance.
>
> S.
>

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