Alternative to loop ifelse() for vector data

Question

I have a price dataframe dat and a second dataframe with currencies cur. What i want to do is to transform every non-EUR price in dat into

Answer 1

I think this would be much easier as a merge/join operation. Using tidy verse you can do

library(tidyverse)
dat <- read_table("Nation   Price
AT       10
AT       12
BE       15
BG       30
BG       40
CZ       200")
cur <- read_table("Nation Rate
BG     0.51
CZ     0.03918")


dat %>% left_join(cur) %>% 
  mutate(Rate=coalesce(Rate, 1)) %>%
  mutate(EPrice = Price * Rate)

The only trick here is to change the Rate for those nations not in the cur table to 1.

Answer 2

The problem with your code is that you are comparing a vector against a character in if (dat$Nation == cur$Nation[i]), so the error tells you that it will only compare the first element of dat$Nation with cur$Nation[i].

In R, for-loops are often not necessary (and slow). You could do for example the following:

dat$conv <- cur$Rate[match(dat$Nation,cur$Nation)] # add the conversion factor
dat$PriceE <- ifelse(is.na(dat$conv), dat$Price, dat$Price * dat$conv)
dat$conv <- NULL

Output:

  Nation Price PriceE
1     AT    10 10.000
2     AT    12 12.000
3     BE    15 15.000
4     BG    30 15.300
5     BG    40 20.400
6     CZ   200  7.836

Hope this helps!