[R] Using data frames for EDA: Insert, Change name, delete columns? (Newcomer's question)

[ronggui]

if i want to rename the data frame,say data1,to data2,have i use those
>data2<-data1
>rm(dat1)
or these is simpler way to do this? thank you !

On Tue, 28 Jun 2005 10:08:55 -0500
"Earl F. Glynn" <efg at stowers-institute.org> wrote:

> "Ben Fairbank" <BEN at SSANET.COM> wrote in message
> news:CA612484A337C6479EA341DF9EEE14AC03AC1BB5 at hercules.ssainfo...
> 
> > I ... cannot find commands to easily insert,
> > remove (delete), rename, and re-order (arbitrarily, not sort) columns.
> ...
> > Could a reader provide a reference where such commands are
> > documented?
> 
> There's a lot of info in the old R-Help postings, but searching and finding
> an answer for a particular problem can be a bit of a pain.
> Here's some info from some old R-Help postings that may help on your
> question:
> 
> DELETE TWO COLUMNS
> -------------------------------------------------------
>  I have a dataframe 'd2004' and I want to remove two columns:
> 'd2004$concentration' and 'd2004$stade".
> 
> I could do it just as follows:
> 
> > names(d2004)
> 
>  [1] "Localite"       "Date"           "parcelle"       "maille"
> "presence.plant" "concentration"  "stade.culture"
>  [8] "stade"          "Trou"           "Horizon"        "Profondeur"
> 
> > d2004 <- d2004[, -c(6, 8)]
> 
> but I'd like to use column names (to avoid finding column numbers each
> time).
> 
> I cannot find an easy way to operate...
> 
> I wonder why that works:
> > d2004[, "concentration"]
> 
> and this don't:
> > d2004 <- d2004[, -c("concentration", "stade")]
> 
> 
> 
> SOLUTIONS:
> 
> d2004$concentration <- NULL
> d2004$stade         <- NULL
> 
> or
> 
> 
> 
> Newdata <- subset(d2004, select=-c(concentration,stade))
> 
> 
> 
> 
> 
> 
> 
> RENAMING COLUMNS
> -------------------------------------------------------
> This is a sample data frame:
> 
> > myData <- data.frame( col1 = 1:3, col2 = 2:4, col3 = 3:5 )
> 
> > myData
> 
>   col1 col2 col3
> 
> 1    1    2    3
> 
> 2    2    3    4
> 
> 3    3    4    5
> 
> 
> 
> You can change all names by:
> 
> > names( myData )<- c( "newcol1", "newcol2", "newcol3" )
> 
> > myData
> 
>   newcol1 newcol2 newcol3
> 
> 1       1       2       3
> 
> 2       2       3       4
> 
> 3       3       4       5
> 
> 
> 
> Or a single name by:
> 
> > names( myData )[ 2 ] <- "newcol2"
> 
> > myData
> 
>   col1 newcol2 col3
> 
> 1    1       2    3
> 
> 2    2       3    4
> 
> 3    3       4    5
> 
> 
> 
> Or if you know the name, but not the column number:
> 
> > names( myData )[ which( names( myData ) == "newcol2" ) ] <- "verynewcol2"
> 
> > myData
> 
>   col1 verynewcol2 col3
> 
> 1    1           2    3
> 
> 2    2           3    4
> 
> 3    3           4    5
> 
> 
> 
> REORDERING COLUMNS
> -------------------------------------------------------
> I don't have a clipping for this one, but here's what I'd try:
> 
> > myData <- data.frame( col1 = 1:3, col2 = 2:4, col3 = 3:5 )
> >
> > myData
>   col1 col2 col3
> 1    1    2    3
> 2    2    3    4
> 3    3    4    5
> > MyData <- myData[,c(3,1,2)]
> > MyData
>   col3 col1 col2
> 1    3    1    2
> 2    4    2    3
> 3    5    3    4
> 
> 
> --
> efg
> Earl F. Glynn
> Bioinformatics
> Stowers Institute for Medical Research
> 
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