R Multiply specific rows and columns by constant

Question

I have the following data:

type <- c(1:4)
year1 <- c(1:4)
year2 <- c(1:4)
year3 <- c(1:4)
data <- data.frame(type, year1, year2, year3)

I want to multiply the bottom two rows within Year columns by two.

type <- c(1:4)
year1 <- c(1, 2, 6, 8)
year2 <- c(1, 2, 6, 8)
year3 <- c(1, 2, 6, 8)
final <- data.frame(type, year1, year2, year3)

How do I do this without affecting the other rows of columns?

Answer 1

Here's a solution using dplyr and tidyr. This would allow you to tweak the parameters if you like.

library(dplyr)
library(tidyr)

newdata <- data %>%
  gather(., year, value, year1:year3) %>%
  mutate(newvalue = ifelse(type > 2, value * 2, value)) %>%
  select(-value) %>%
  spread(., year, newvalue)