Question

df <- data.frame(dive=factor(sample(c("dive1","dive2", "dive3"),20,replace=TRUE)),speed=runif(20))
> df
    dive      speed   Drift
1  dive1 0.80668490    TRUE
2  dive1 0.53349584    FALSE
3  dive2 0.07571784    TRUE
4  dive2 0.39518628    TRUE
5  dive1 0.84557955    TRUE
6  dive1 0.69121443    FALSE
7  dive1 0.38124950    TRUE
8  dive2 0.22536126    FALSE
9  dive1 0.04704750    FALSE
10 dive2 0.93561651    TRUE

Suppose I have a data frame of this form with a third column named “Drift” where the row values are either “TRUE” or “FALSE”. How would I go about working out the percentage of rows equal to TRUE when “dive” equals a specific value. I.e. when dive==1 what percentage of the “drift” column is “TRUE”?
Thankyou.

Answer 1

You could try:

df$Drift <- c(T,F)
sapply(split(df, df$dive), function(x) sum(x$Drift) / nrow(x) * 100 ) 
   dive1    dive2    dive3 
57.14286 42.85714 50.00000