[R] function doesn't change the variable in the right way

[Rui Barradas]

Hello,

Inline.

Em 07-03-2014 11:17, David Croll escreveu:
>
> Dear R users and friends,
>
>
> I would like to ask you about the weird behaviour of a function I just
> wrote. This little function should take a vector, find NAs and
> substitute them for the mean of the vector, and return the normalized
> value of that vector.
>
> I've tried both <- and <<- for changing the variables.
>
> That's what I do:
>
> # just a vector:
> b <- c(1,1,1,NA,3,2)
>
> # my function:
> normalize <- function(x) {
>
>      # copy x into new vector
>      xn <- x
>
>      # index of NAs
>      nas <- which(is.na(xn) ==TRUE)
>      m <- mean(xn, na.rm=TRUE)
>
>      # insert mean for NAs
>      xn[nas] <- m
>
>      # normalize
>      return((xn - mean(xn))/sd(xn))
>
> }
>
> # run...
> normalize(b)
>
> # here's what I get:
> # [1] -0.75 -0.75 -0.75  0.00  1.75  0.50
>
>
> The 4th value should be 1.6, but is 0.

No it shouldn't. The value of the 4th element should be 0. It is equal 
to mean(xn, na.rm = TRUE) - mean(new xn) and this is zero.

Hope this helps,

Rui Barradas
>
>
> I believe the answer to my problem is pretty obvious, but I can't see it...
>
>
> Best regards,
>
>
> David
>
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