How do I change contents of a column in data.frame - r

Question

I’m using data from World Development Indicators (WDI) and want to merge this data with some other data. My problem is that the spelling of country names in the two datasets is different. How do I change the country variable?
library('WDI')
df <- WDI(country="all", indicator= c("NY.GDP.MKTP.CD", "EN.ATM.CO2E.KD.GD", 'SE.TER.ENRR'), start=1998, end=2011, extra=FALSE)
head(df)
country iso2c year NY.GDP.MKTP.CD EN.ATM.CO2E.KD.GD SE.TER.ENRR
99 ArabWorld 1A 1998 575369488074 1.365953 NA
100 ArabWorld 1A 1999 627550544566 1.355583 19.54259
101 ArabWorld 1A 2000 723111925659 1.476619 NA
102 ArabWorld 1A 2001 703688747656 1.412750 NA
103 ArabWorld 1A 2002 713021728054 1.413733 NA
104 ArabWorld 1A 2003 803017236111 1.469197 NA
How do i change ArabWorld to Arab World?
There are a lot of names I need to change so doing this with the use of row.numbers will not give me enough flexibility. I want something that is similar to the replace function in Stata.

Answer 1

This would work for character or factors.
df$country <- sub("ArabWorld", "Arab World", df$country)
This is equivalent:
> df[,1] <- sub("ArabWorld", "Arab World", df[,1] )
> head(df)
country iso2c year NY.GDP.MKTP.CD EN.ATM.CO2E.KD.GD
99 Arab World 1A 1998 575369488074 1.365953
100 Arab World 1A 1999 627550544566 1.355583
101 Arab World 1A 2000 723111925659 1.476619
102 Arab World 1A 2001 703688747656 1.412750
If you create a dataframe with the desired changes you can loop through to change them. Note that I have updated this so that it shows how to enter the parentheses in that column so they would be correctly passed to sub:
name.cng <- data.frame(orig = c("AntiguaandBarbuda", "AmericanSamoa",
"EastAsia&Pacific\\(developingonly\\)",
"Europe&CentralAsia\\(developingonly\\)",
"UnitedArabEmirates"),
spaced=c("Antigua and Barbuda", "American Samoa",
"East Asia & Pacific (developing only)",
"Europe&CentralAsia (developing only)",
"United Arab Emirates") )
for (i in 1:NROW(name.cng)){
df$country <- sub(name.cng[i,1], name.cng[i,2], df$country) }

Answer 2

The easiest, especially if you have many names to change, is probably to put your correspondance table in a data.frame, and join it with the data, with the merge command.
For instance, if you wanted to change the name of the Koreas:
# Correspondance table
countries <- data.frame(
iso2c = c("KR", "KP"),
country = c("South Korea", "North Korea")
)
# Join the data.frames
d <- merge( df, countries, by="iso2c", all.x=TRUE )
# Compute the new country name
d$country <- ifelse(is.na(d$country.y), as.character(d$country.x), as.character(d$country.y))
# Remove the columns we no longer need
d <- d[, setdiff(names(d), c("country.x", "country.y"))]
# Check that the result looks correct
head(d)
head(d[ d$iso2c %in% c("KR", "KP"), ])
However, it may be safer to join your two datasets on the country ISO code, which is more standard, than on the country name.

Answer 3

Using subsetting:
df[df[, "country"] == "ArabWorld", "country"] <- "Arab World"
head(df)
country iso2c year NY.GDP.MKTP.CD EN.ATM.CO2E.KD.GD SE.TER.ENRR
99 Arab World 1A 1998 575369488074 1.365953 NA
100 Arab World 1A 1999 627550544566 1.355583 19.54259
101 Arab World 1A 2000 723111925659 1.476619 NA
102 Arab World 1A 2001 703688747656 1.412750 NA
103 Arab World 1A 2002 713021728054 1.413733 NA
104 Arab World 1A 2003 803017236111 1.469197 NA