Multiply columns with rows by matching column name and row name in R

Question

I have a data frame which looks like this

> data
  A B
1 1 2
2 2 1

I have a reference data frame which looks like this

> ref
  Names Values
1     A      5
2     B     10

I want to multiply each column by corresponding row in Ref having same Name

the result should be this

> result
   A  B
1  5 20
2 10 10

What is the fastest way to achieve this in R? Any help would be greatly appreciated

Answer 1

We can match the column names of 'data' with 'Names' column of 'ref', get the corresponding 'Values' based on the numeric index and then multiply by replicating the ref$Values

data*ref$Values[match(names(data), ref$Names)][col(data)]
#   A  B
#1  5 20
#2 10 10

Answer 2

If you use Names for rownames instead in ref , you could do something like this as well

rownames(ref) <- ref$Names #assign rownames
ref$Names <- NULL #drop col

i <- intersect(rownames(ref), colnames(data)) #find intersect
mapply(`*`, ref[i, ], data[, i]) #perform multiplication
#     [,1] [,2]
#[1,]    5   20
#[2,]   10   10

Answer 3

this should work:

for (n in seq(along = names(data))) {
    data[,n] <- data[,n] * ref$Values[which(ref$Names == names(data)[n])]
}