On Apr 28, 2012, at 10:46 AM, Daniel Malter wrote:
Hi,
I have a data frame whose first row (not the header) contains the true
column names. The same column name can occur multiple times in the
dataset.
Columns with equal names are not adjacent, and for each observation
only one
of the equally named columns contains the actual data (see the example
below). I am looking for an easy method consolidate these columns
into one
column for each unique column name. Say,
x1<-c("x",1,NA,NA)
x2<-c("x",NA,2,NA)
x3<-c("x",NA,NA,3)
y1<-c("y",3,NA,NA)
y2<-c("y",NA,1,NA)
y3<-c("y",NA,NA,2)
d<-data.frame(x1,y1,x2,y2,x3,y3)
d
It would avoid problems with manipulating factors it these were
created (or converted to) character columns, choose one of:
d=data.frame(x1,y1,x2,y2,x3,y3, stringsAsFactors=FALSE)
d[]<-lapply(d, as.character)
# d looks like:
x1 y1 x2 y2 x3 y3
1 x y x y x y
2 1 3 <NA> <NA> <NA> <NA>
3 <NA> <NA> 2 1 <NA> <NA>
4 <NA> <NA> <NA> <NA> 3 2
From this, I want to create the table or data frame
x y
1 3
2 1
3 2
na.omit(
data.frame(
X=stack(d[-1,grep("x", names(d))]),
Y=stack(d[-1,grep("y", names(d))]),
stringsAsFactors=FALSE)[ c(1,3) ])
X.values Y.values
1 1 3
5 2 1
9 3 2
If it were less regular you might need to merge with the "source"
columns that stack generates.
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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