[R] Warning: number of items to replace is not a multiple of replacement length

[Barry Rowlingson]

Mag. Ferri Leberl wrote:
> What does this warning mean precisely?

When R replaces parts of a vector with another vector, it repeats the 
replacing value until it is as long as the number of values it needs to 
replace. For example:

  > x = 1:10
  > x[1:3]=1

   - will do, effectively, x[1:3] = rep(1,3)

  Now, if you replace with a vector that isn't an integer multiple of 
the things being replaced, you get that error:

  > x[1:3]=c(1,2)
  Warning message:
  number of items to replace is not a multiple of replacement length

  Note that if it is an integer multiple, you don't get the error:

  > x[1:6]=c(1,2)

  but it repeats the (1,2) 3 times to fill the six places:

  > x
   [1]  1  2  1  2  1  2  7  8  9 10


> Is there any reason to care about it?

  Yes, it usually means you've specified something wrong. What have you 
done?

Baz