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bcorso
bcorso

Reputation: 47058

R : Map a column to column using key-value list

In R, I want to use a key-value list to convert a column of keys to values. It's similar to: How to map a column through a dictionary in R, but I want to use a list not a data.frame.

I've tried to do this using list and columns:

d = list('a'=1, 'b'=2, 'c'=3)
d[c('a', 'a', 'c', 'b')]  # I want this to return c(1,1,3,2) but it doesn't

However, the above returns a list:

list('a'=1, 'a'=1, 'c'=3, 'b'=2)

Upvotes: 2

Views: 3553

Answers (1)

akrun
akrun

Reputation: 886948

unlist is a useful function in this situation

unlist(d[c('a', 'a', 'c', 'b')], use.names=FALSE)
#[1] 1 1 3 2

Or another option is stack which returns the 'key/value' as columns in a 'data.frame'. By subsetting the values column, we get

stack( d[c('a', 'a', 'c', 'b')])[,1]
#[1] 1 1 3 2

Upvotes: 4

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