R: Recoding Variables Across Multiple Objects - r

Question

Thank you in advance for your advice. I am trying to create a new variable over multiple objects in a loop. These new variables are generated by a function.
For example, I have three sets of country-level data:
# Generate Example Data
`enter code here`pop <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(290,300,29,30,50,55))
gas <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(3.10,1.80,4.50,2.50,4.50,2.50))
cars <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(2.1,2.2,1.8,1.9,1.3,1.3))
I want to create a new variable, called “countrycode”, using the countrycode() command in the countrycode package.
I would perform the operation on individual objects like this:
library(countrycode)
pop$ccode <- countrycode(pop$country,"iso2c","cown")
pop$id <- (pop$ccode*10000)+pop$year
But I have a large number of objects. I was hoping to do this over a loop, like this
# Create list of variables
vars <- c("pop","gas","cars")
for (i in vars){
i$ccode <- countrycode(country,"iso2c","cown")
i$id <- (i$ccode*10000)+i$year
}
But that doesn’t work. I’ve been trying to do this using assign() in loops and apply(), but I’m too dense to get my head around how to make this work in my case.
If someone could provide me with an example of how to do this with my own type of data, I’d be very grateful.

Answer 1

Would this work for you?
pop <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(290,300,29,30,50,55))
gas <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(3.10,1.80,4.50,2.50,4.50,2.50))
cars <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(2.1,2.2,1.8,1.9,1.3,1.3))
attachCodes <- function(dframe)
{
df <- dframe
df$ccode <- countrycode(df$country,"iso2c","cown")
df$id <- (df$ccode*10000)+df$year
return(df)
}
tablesList <- list(pop,gas,cars)
tablesList <- lapply(tablesList,attachCodes)

Answer 2

Special thanks to #Pawel for supplying the missing information needed to solve the problem. The solution was:
rm(list=ls())
pop <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(290,300,29,30,50,55))
gas <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(3.10,1.80,4.50,2.50,4.50,2.50))
cars <- data.frame(country=c("US","US","CA","CA","FR","FR"),year=c(1,2,1,2,1,2),value=c(2.1,2.2,1.8,1.9,1.3,1.3))
attachCodes <- function(dframe)
{
df <- dframe
df$ccode <- countrycode(df$country,"iso2c","cown")
df$id <- (df$ccode*10000)+df$year
return(df)
}
names <- list("pop","gas","cars")
for(i in names){
assign(i,attachCodes(get(i)))
}