Question

i have a data frame, which looks like this, but huge so I can’t do anything manually:

   Bank  Country  KeyItem    Year    Value 
    A      AU     Income     2010     1000
    A      AU     Income     2011     1130
    A      AU     Income     2012     1160
    B      USA    Depth      2010     10000

What I want to do is create a function where I can select the Bank, the Keyitem and from which year onwards and it returns a dataframe with the values as percentage of the first value . Like this:

   Bank  Country  KeyItem    Year    Value
    A      AU     Income     2010     100
    A      AU     Income     2011     113
    A      AU     Income     2012     116

Thank you in advance!

Answer 1

Try the following approach: (df is your data frame)

Choose the criteria:

bank <- "A"
keyItem <- "Income"
year <- 2011

Create a subset:

dat <- subset(df, Bank == bank & KeyItem == keyItem & Year >= year)

Calculate percentages:

dat$Value <- dat$Value / dat$Value[1] * 100

As a function:

myfun <- function(df, bank, keyItem, year) {
   dat <- df[df$Bank == bank & df$KeyItem == keyItem & df$Year >= year, ]
   "[[<-"(dat, "Value", value = dat$Value / dat$Value[1] * 100)
}

myfun(df, "A", "Income", 2011)