R help - Mar 2014 - function doesn't change the variable in the right way

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.


I believe the answer to my problem is pretty obvious, but I can't see it...


Best regards,


David

Hello

The function does exactly what you tell it to do; first you substitute 
all NA with the mean; then you subtract the mean;  for the NA this 
meand: mean-mean=0; and this is what you get.

the problem is not the function but the z-score of means.

lg fabian

On 07-03-2014 12:17, David Croll wrote:
> 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.
> 
> 
> I believe the answer to my problem is pretty obvious, but I can't see 
> it...
> 
> 
> Best regards,
> 
> 
> David
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.