[R] how do i vectorize relational queries in R
Don MacQueen
macq at llnl.gov
Thu Aug 20 01:42:54 CEST 2009
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???
>--
>View this message in context:
>http://*www.*nabble.com/how-do-i-vectorize-relational-queries-in-R-tp25052929p25052929.html
>Sent from the R help mailing list archive at Nabble.com.
>
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--
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
925-423-1062
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