[R] If statements for multiple arrays

[David Winsemius]

I see Joshua has kindly offered some resources to turn you from your  
path of erroR and sins against the interpreteR, but if you want to do  
extra penance, you might consider reading the R-FAQ (although your  
issue if if and "&&" is surprisingly not included there) :

http://cran.r-project.org/doc/FAQ/R-FAQ.html
http://cran.r-project.org/doc/FAQ/R-FAQ.html#R-Miscellanea

Then depending on the level of further contRition you might want to  
exert, you could also read the "R Inferno"
(Abstract: If you are using R and you think you’re in hell, this is a  
map for you.)  by Patrick Burns:

http://www.burns-stat.com/pages/Tutor/R_inferno.pdf  (see section 3.2  
for your problem)

-- 
David.

On Sep 16, 2010, at 4:51 PM, George Coyle wrote:

> Hello,
>
> I wrote this code which works fine on a single observation:
>
> x<-100
> y<-200
> z<-125
> aa<-150
> if(x<z && y>z) {aa-z}
> result: 25
>
> I am trying to apply this logic where x,y,z,and aa are arrays but  
> with very
> little success.  I have tried using loops and whiles but I always  
> get errors
> of various types.  I have consulted a few manuals but with limited  
> success.
> My hopeful outcome would be:
>
> data:
>    X       Y      Z      AA
> 1 100  200    125     150
> 2 125   110    105    140
> 3 110    150   130    200
> 4 90    200     75    65
>
> Here row 1 would return 25, row 2 would return nothing since Z<X,  
> row 3
> would be 50, row 4 would be nothing since X>Z.
>
> In this case I am trying to return something where I could call the  
> output a
> variable "Z" which would become an array based on the logic above  
> where the
> members would be: (25, 50)
>
> I tried using this where the variables are arrays:
> if(x<z && y>z) {aa-z}
> But I get "NULL"
>
> I tried using this where the variables are arrays:
> if(x<z && y>z) {aa-z} else "NA"
> But I get "NA"
>
> When I tried using a loop:
> for(i in 1:length(x)) if(x<z && y>z) {aa-z} else "NA"
> I got "NULL"
>
> An attempt at a "while" statement crashed.
>
> The time series resource (
> http://cran.r-project.org/doc/contrib/Ricci-refcard-ts.pdf) is way too
> involved.  Most online sources I am finding are not good for "if"  
> contingent
> array manipulation.  Annoyingly, just saying aa-z will work across the
> entire array but for some reason my ifs fail.  I know the R help  
> group only
> wants serious emails so hopefully this will indicate I gave it a
> reasonable shot.
>
> Please help
>
> Thanks
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.

David Winsemius, MD
West Hartford, CT