Jonathan Flowers wrote:
Hi,
I would like to extract columns from a dataframe using a vector of desired
column names.
The following working example uses the select argument in the subset
function to accomplish what I am trying to do. Is there a better solution?
This is very much "Introduction to R" stuff.
A word of warning: both 'data' and 'colnames' are built-in functions, so
you may not want to call your variables those things to avoid confusion.
After your definitions below, try:
> data[colnames]
> data$col1
> data$col3
> data[["col1"]]
> data[["col3"]]
compare the previous two with:
> data["col1"]
> data["col3"]
Thanks.
#my data
data <- data.frame("col1"=c(1,2,3),"col2"=c("A","B","C"),"col3"=c(4,5,6))
#names of desired columns
colnames <- c("col1","col3")
fun <- function(colname,dframe){
nframe <- subset(dframe,select=colname)
vec <- nframe[,1]
return(vec)
}
fun(colnames[1],data)
fun(colnames[2],data)
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