Loop over string variables in R

Question

When programming in Stata I often find myself using the loop index in the programming. For example, I\'ll loop over a list of the variables nominalprice and realprice:

Answer 1

I don't see what's especially wrong with your original solution, except that I don't know why you're using the eval() function. That doesn't seem necessary to me.

You can also use an apply function, such as lapply. Here's a working example. I created dummy data as a zoo() time series (this isn't necessary, but since you're working with time series data anyway):

# x <- some time series data
time <- as.Date("2003-02-01") + c(1, 3, 7, 9, 14) - 1
x <- zoo(data.frame(nominalprice=rnorm(5),realprice=rnorm(5)), time)
lapply(c("nominalprice", "realprice"), function(c.name, x) { 
  png(paste("c:/TimePlot-", c.name, ".png", sep=""))
  plot(x[,c.name], main=c.name)
  dev.off()
}, x=x)