Rank the dataframe values in R

Question

I want to fetch the row numbers of the first 5 highest values in a column in a dataframe and add a value of 100 on the same row number in another dataframe and rest other values as 0.

I know how to sort / order a column in a dataframe using order() function.

df=data.frame(a=c(345,948,290,189,3848,302,384,456,383,201,35,346,1.46,4.66,3,5,63,43,6432,4336,345,354,1245,342,523,743,248,932.5))

For example, df[order(-df$a),] results in

6432.00 4336.00 3848.00 1245.00  948.00  932.50  743.00  523.00  456.00  384.00  383.00  354.00 346.00  345.00  345.00  342.00  302.00  290.00  248.00  201.00  189.00   63.00   43.00   35.00   5.00    4.66    3.00    1.46 

However, I am not able to meet my specific requirement.

I would expect to see df1 as

0 100 0 0 100 0 0 0 0 0 0 0 0 0 0 0 0 0 100 100 0 0 100 0 0 0 0 0

Answer 1

We could use the rank function:

df$b <- (rank(-df$a) <= 5) * 100

Answer 2

df$b <- ifelse(df$a %in% sort(df$a, T)[1:5], 100, 0)