Does
merge(data,meta)
give what you want?
FWIW:
"append" to a dataframe would normally mean to add more rows (or at
least that's how I use it), but you appear to be adding a column.
"data" is the name of an R function, best avoided for other uses.
You're assigning the column names the hard way. Try
mydata <- data.frame(Sample=c(1,1,1,2,2,2,3,3,3), Score=rep(2,9))
To avoid the factors, use
meta <- data.frame(Score=c(1,2,3), Stratum = I(c("Tree","Tree","Shrub")) )
## that's an upper case letter "i" in I()
or
meta <- data.frame(Score=c(1,2,3), Stratum =
c("Tree","Tree","Shrub"), stringsAsFactors=FALSE )
## easily found in the help page for data.frame
-Don
At 3:21 PM -0700 8/19/09, chipmaney wrote:
I am basically trying to append a value(vector) to one dataframe using a
relational value from another dataframe. Obviously, I can use a loop to
accomplish this. However, is there a way to vectorize it?
Example:
> data <- data.frame(c(1,1,1,2,2,2,3,3,3),rep(2,9)); names(data) <-
c("Sample","Score")
> meta <- data.frame(c(1,2,3),c("Tree","Tree","Shrub")); names(meta) <-
c("Sample","Stratum")
The following attempt at vectorizaton doesn't work:
data$Stratum <- meta$Stratum[which(data$Sample == meta$Sample)]
data$Stratum
[1] Tree <NA> <NA> Tree <NA> <NA> Tree <NA> <NA>
And actually, when I try to run a loop, the operation converts the string to
a factor.
for (i in 1:length(data[,1])) data$Stratum[i] <-
meta$Stratum[which(meta$Sample == data$Sample[i])]
data
Sample Score Stratum
1 1 2 2
2 1 2 2
3 1 2 2
4 2 2 2
5 2 2 2
6 2 2 2
7 3 2 1
8 3 2 1
9 3 2 1
Argghhhh....I don't want a factor, and anyway I don't want to use a loop...
Can anyone help with these two issues???
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--
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
925-423-1062
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