R: Sort columns of a data frame by a vector of column names

Question

I have a data.frame that looks like this:

which has 1000+ columns with similar

Answer 1

A5C1D2H2I1M1N2O1R2T1's solution didn't work for my data (I've a similar problem that Yilun Zhang) so I found another option:

mydf <- data.frame(A = 1:2, B = 3:4, C = 5:6)
#   A B C
# 1 1 3 5
# 2 2 4 6
matches <- c("B", "C", "A") #desired order

mydf_reorder <- mydf[,match(matches, colnames(mydf))]
colnames(mydf_reorder)
#[1] "B" "C" "A"

match() find the the position of first element on the second one:

match(matches, colnames(mydf))
#[1] 2 3 1

I hope this can offer another solution if anyone is having problems!