Question

I have a two column dataframe in R and i want to add a third column with values that are a function of the first two.
As long as the function is a simple mathematical formula no problem
data$c <- data$a*15 - 10 + data$b*0.5
But my function is non continous and contains conditionals, i would like to do:
foo <- function(x,y){if (x<2) {return(0)} else {....}
and
data$c <- foo(data$a, data$b)
But this gets me errors. What am i missing?

Answer 1

df = data.frame(a=rnorm(20),b=runif(20))

new_var = function(x,y)
{
  if(x<0)
  { x = x^2}
  else
  { x = x^3}

  if(y<.5)
  { -log10(y)}
  else
  {
    exp(y)
  }
  return((2*(x+y))/x*y)
}

df$c = sapply(1:length(df$a), function(i){new_var(df$a[i],df$b[i])})

head(df)
            a          b          c
1 -0.09149107 0.04834675 0.65517298
2 -2.43732351 0.04086087 0.08228385
3 -1.69573283 0.54795413 1.30474339
4 -0.40106220 0.72952356 8.07641367
5 -0.38244706 0.65524147 7.18118555
6  0.76334945 0.38455655 1.43404971