Replace many strings by their counterparts according to a mapping

Question

I have a vector of strings (e.g. country names), and a mapping of those strings to other strings (e.g. a mapping of country names to iso codes).

countries = c('United States', 'Ecuador', 'Russia', 'Russia', 'Ecuador')
mapping = data.frame(country = c('Ecuador', 'Russia', 'United States'),
                     iso3 = c('ECU', 'RUS', 'USA'))

How can I replace all occurences of country names in countries by the respective iso codes according to mapping?

You can use `factor` and `levels`. – Justin Jun 14 '13 at 14:27 — Justin, Jun 14 '13 at 14:27

score 8 · Answer 1 · answered Jun 14 '13 at 14:32

8

This is one way:

with(mapping, iso3[match(countries, country)])
# [1] USA ECU RUS RUS ECU
# Levels: ECU RUS USA

Wrap this in as.character to the result as a character vector.

answered Jun 14 '13 at 14:32

Matthew Plourde

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score 4 · Accepted Answer · answered Jun 14 '13 at 14:34

4

Alternatively, as Justin pointed out:

factor(countries,levels = mapping$country,labels = mapping$iso3)
[1] USA ECU RUS RUS ECU
Levels: ECU RUS USA

answered Jun 14 '13 at 14:34

joran

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Thanks! I accepted this answer because it helped me to realize that I should be using factors for this variable. @Matthews answer works just as well, however. – severin Jun 14 '13 at 14:44

Replace many strings by their counterparts according to a mapping

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