Read the help file on how to extract from a data frame:
?"[.data.frame"
Then, try adding a comma inside the brackets.
data.station1 <- data[data$Station==1, ]
Before the comma, the data$Station==1 identifies what rows to select.
After the comma, the lack of specification indicates that all columns
should be selected.
Jean
Suzanne.mertens wrote on 01/17/2012 03:17:41 PM:
> (As a noob to R, this is my first posting - yes yes, groans all
around...)
>
> I'm trying to extract certain rows from a data frame. I used the
> following to import data from a CSV txt file.
>
> data <- read.table(file="data.txt", header=TRUE)
>
> when I do this, my attempt to extract the data rows only from where
> the Station value equals 1?
>
> data.station1 <- data[data$Station == 1]
>
> ...is giving me the following error message:
>
> Error in `[.data.frame`(data, data
> $Station == 1) :
> undefined columns selected
>
>
> Bah.
> If I use names(data) I can see "Station" as a column name.
> And if I use str(data), the variable "Station" is coming up as
> integers including the value 1.
> And if I use data$Station, I see all station values, including the 1s.
> And if I use data[,"Station"] I do see all the Station values
> And if I instead treat the Station values as characters, by using
> "1", I still get the "undefined" error.
>
> Could someone please correct me on my syntax? Or advise if perhaps I
> imported the data the wrong way? I'm working out of "A Beginner's
> Guide to R" and also looked through the R manual, and even tried
> this from Google search:
>
> data.station1 <- data,("Station" == 1) ]
>
> But that gave me an unwanted output:
> data frame with 0 columns and 789 rows
>
> Almost, but not quite. Please help?
>
>
> Thank you,
>
>
>
> - Suzanne
> ..........................................
> suzanne.mert...@gmail.com
> 404-337-1533
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