Question

Suppose, I have a data set like,

y <- c(0,0,1,2,2,1,0,1)
a <- c(0,2,1,1,0,2,0,3)
dat <- data.frame(y, a)

I want to calculate the value of f <- digamma(a+y) by using the condition

if(a>0 & y==0) then f
if(a==0 & y>0) then f
if (a==0 & y==0) then f = 1

How can I do it using R code?

Answer 1

I think this will give you what you’re after post hoc:

f <- digamma(a+y) 
f[a==0 & y==0] <- 1

or

f[is.nan(f)] <- 1

Well this is using indexing to see which elements in the vector are nan or in the first method both a and y are 0. Then the index [] says take these elements of f and the assignment <- says make these elements a one.