[R] How to change the order of columns in a data frame?
Petr Savicky
savicky at cs.cas.cz
Fri Feb 17 14:46:57 CET 2012
On Fri, Feb 17, 2012 at 02:26:52PM +0100, Joel Fürstenberg-Hägg wrote:
> Dear all,
>
> I have a data frame in which the columns need to be ordered. The first column X is at the right position, but the remaining columns X1-Xn should be ordered like this: X1, X2, X3 etc instead of like below.
>
> > colnames(pos1)
> [1] "X" "X1" "X10" "X11" "X12" "X13" "X14" "X15" "X16" "X17" "X18" "X19" "X2" "X20" "X3" "X4" "X5" "X6" "X7" "X8" "X9"
>
> > pos1[1:5,1:5]
> X X1 X10 X11 X12
> 1 100.5 7949.469 18509.064 8484.969 17401.056
> 2 101.5 3080.058 7794.691 3211.323 8211.058
> 3 102.5 1854.347 4347.571 1783.846 4827.338
> 4 103.5 2064.441 8421.746 2012.536 8363.785
> 5 104.5 9650.402 26637.926 10730.647 27053.421
>
> I am trying to first change the first column name to something without an X and save as a vector. I would then remove the X from each position use the vector for renaming the columns. Then the column 2-n could be ordered, I hope...
>
> colnames(pos)[1] <- "Mass"
> columnNames <- colnames(pos)
Hi.
Try the following. For simplicity, i assume the first
column to be X0, but this is not necessary. Example data
a <- sort(paste("A", 0:19, sep=""))
names(a) <- sort(paste("X", 0:19, sep=""))
pos <- data.frame(rbind(a))
pos
X0 X1 X10 X11 X12 X13 X14 X15 X16 X17 X18 X19 X2 X3 X4 X5 X6 X7 X8 X9
a A0 A1 A10 A11 A12 A13 A14 A15 A16 A17 A18 A19 A2 A3 A4 A5 A6 A7 A8 A9
The reordering:
columnNames <- colnames(pos)
ind <- as.integer(substr(columnNames, 2, nchar(columnNames)))
pos[, order(ind)]
X0 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12 X13 X14 X15 X16 X17 X18 X19
a A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 A16 A17 A18 A19
Hope this helps.
Petr Savicky.
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