On Jan 17, 2012, at 4:56 PM, Jean V Adams wrote:
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.
And if you want to avoid getting all the rows where data$Station are
NA, then use either of these alternatives resulting in what I expect
and generally want to see as a result:
data.station1 <- subset( data, Station==1 )
data.station1 <- data[ which(data$Station==1) , ]
--
David.
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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