[R] Thanks!

[R_Learner]

Thanks guys!
I think [[ seems to be the easier way, but I also spent an hour (while my
post was pending approval) to find that the following also works:

temp<- eval(parse(text=paste("data$column_title"")))


Marc Schwartz wrote:
> 
> on 07/02/2008 02:10 PM R_Learner wrote:
>> raw <- read.csv(file=filename, head=TRUE,sep=",") 
>> 
>> I've read in a csv file, and I'm looking to access a column whose name is
>> held in a string.
>> 
>> For example, I want to access raw$one or raw$two, but this will depending
>> on
>> the string. Let's say that the string is decision<-"one". How would I
>> access
>> raw$one?
>> 
>> The following doesn't work:
>> numbers<-raw$decision
>> 
>> Please help me!
>> Thanks!
> 
> 
>  > str(iris)
> 'data.frame':	150 obs. of  5 variables:
>   $ Sepal.Length: num  5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
>   $ Sepal.Width : num  3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
>   $ Petal.Length: num  1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ...
>   $ Petal.Width : num  0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ...
>   $ Species     : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 
> 1 1 1 1 1 ...
> 
> 
> MyCol <- "Petal.Length"
> 
> 
> # Use column indexing
>  > iris[, MyCol]
>    [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5
>   [17] 1.3 1.4 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5
> ...
> 
> # Use list indexing. A data frame is a list...
>  > iris[[MyCol]]
>    [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2 1.5
>   [17] 1.3 1.4 1.7 1.5 1.7 1.5 1.0 1.7 1.9 1.6 1.6 1.5 1.4 1.6 1.6 1.5
> 
> 
> # Use subset()
>  > subset(iris, select = MyCol)
>      Petal.Length
> 1            1.4
> 2            1.4
> 3            1.3
> 4            1.5
> 5            1.4
> ...
> 
> 
> See ?"[.data.frame" and ?subset
> 
> 
> HTH,
> 
> Marc Schwartz
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> 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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