Change column values based on factors of other columns

Question

For example, if I have a data frame like this:

df <- data.frame(profit=c(10,10,10), year=c(2010,2011,2012))

profit     year  
10         2010  
10         2011  
10         2012 

I want to change the value of profit according to the year . For year 2010, I multiple the profit by 3, for year 2011, multiple the profit by 4, for year 2012, multiple by 5, which should result like this:

profit     year  
30         2010  
40         2011  
50         2012 

How should I approach this? I tried:

inflationtransform <- function(k,v) {
    switch(k, 
        2010,v<-v*3,
        2011,v<-v*4,
        2012,v<-v*5,
    )
}

df$profit <- sapply(df$year,df$profit,inflationtransform)

But it doesn't work. Can someone tell me what to do?

Answer 1

For this particular example, since your factors and years are both ordered and incremented by 1, you could just subtract 2007 from the year column and multiply it by profit .

transform(df, profit = profit * (year - 2007))
#   profit year
# 1     30 2010
# 2     40 2011
# 3     50 2012 

Otherwise, you could use a lookup vector. This will cover all cases.

lookup <- c("2010" = 3, "2011" = 4, "2012" = 5)
transform(df, profit = profit * lookup[as.character(year)])
#   profit year
# 1     30 2010
# 2     40 2011
# 3     50 2012

I wouldn't use switch() unless you really need to. It's not vectorized, and that's where R is most efficient. However, since you ask for it in the comments, here's one way. I find it easier to use a for() loop with switch() .

for(i in seq_len(nrow(df))) {
    df$profit[i] <- with(df, switch(as.character(year[i]),
        "2010" = 3 * profit[i],
        "2011" = 4 * profit[i],
        "2012" = 5 * profit[i]
    ))
}