How to write multiple if statement R

Question

I am manipulating raster data in R with the rgdal and raster packages. I want to get rid of all infinite, no values, negative values and replace them with zero:

NoNA <- function (x) { 
    x[is.infinite(x) | is.na(x) | is.nan(x) | is.null(x) | is.na(x < 0)] <- 0
}
ndii_noNA <- calc(ndii, NoNA)

Then the ndii_noNA have only a value of 0. I tried if else statement but it raises an error in

.calcTest(x[1:5], fun, na.rm, forcefun, forceapply).

Is there any way to solve this?

Answer 1

You are very close, but have made two errors:

1. You need to use which() in the index of x, rather than just the truth statement. Otherwise, you will index either x[TRUE] or x[FALSE], which is not what you want. which() will return the indices of all "bad" elements in your vector.
2. When you make the assignment with <-, the local copy of x will be changed, not the one that was passed. If you want to change x in place, you need to use <<-. That said, you would be wise to stick to R's functional paradigm, in which you would make the change to the local copy, then return it with return(x), rather than change in place.

Here is the function you want:

# The "change in place" method (may be considered bad style)
NoNA <- function(x) {
  x[which(is.infinite(x) | is.na(x) | is.nan(x) | is.null(x) | is.na(x < 0))] <<- 0
}
# The functional way (recommended)
NoNA <- function(x) {
  x[which(is.infinite(x) | is.na(x) | is.nan(x) | is.null(x) | is.na(x < 0))] <- 0
  return(x)
}