[R] binary operators that never return missing values

[Anthony Damico]

Thanks Michael,

I was hoping to complete this in one step (since I use these a lot).
Setting the class of the vectors seems like more typing than just
doing %>F%  ...

Unfortunately, my knowledge of classes, methods, and the like is
pretty shaky.  Is it possible to *create* another set of operators
that just changes NAs to falses or trues?--

>F  <F  >=F  <=F  >T  <T  >=T  <=T

I definitely don't want to change the base functionality of the
operators, so infix notation seems like the strategy that will require
the least typing in the long run..  but my mind is still open. :)



On Wed, Jun 20, 2012 at 4:54 PM, R. Michael Weylandt
<michael.weylandt at gmail.com> wrote:
> Hi Anthony,
>
> No, I don't believe this exists on CRAN already (happy to be proven
> wrong though) but I might suggest you approach things a different way:
> instead of defining this operator by operator with infix notation, why
> not go after `+`, `>` directly? If you put a class on your vectors,
> you can define Ops.class which will change the behavior of all those
> sorts of things.
>
> Simple example (probably not complete nor necessarily advisable)
>
> a <- c( 1 , NA , 7 , 2 , NA )
> b <- c( NA , NA , 9 , 1 , 6 )
>
> class(a) <- class(b) <- "damico"
>
> Ops.damico <- function(e1, e2 = NULL){
>    e1[is.na(e1)] <- 0
>    e2[is.na(e2)] <- 0
>    NextMethod()
> }
>
> a < b
>
> More nuance is available, but this hopefully gives you a start. You
> might, e.g., think about setting this as something more like:
>
> Ops.damico <- function(e1, e2 = NULL){
>    if(.Generic %in% c("==","!=","<","<=",">=",">")){
>        e1[is.na(e1)] <- 0
>        e2[is.na(e2)] <- 0
>    }
>    NextMethod()
> }
>
> so you don't mess up arithmetic but only the boolean comparisons.
>
> Best,
> Michael
>
> On Wed, Jun 20, 2012 at 3:44 PM, Anthony Damico <ajdamico at gmail.com> wrote:
>> Hi, I work with data sets with lots of missing values.  We often need
>> to conduct logical tests on numeric vectors containing missing values.
>>  I've searched around for material and conversations on this topic,
>> but I'm having a hard time finding anything.  Has anyone written a
>> package that deals with this sort of thing?  All I want are a group of
>> functions like the ones I've posted below, but I'm worried I'm
>> re-inventing the wheel..  If they're not already on CRAN, I feel like
>> I should add them.  Any pointers to work already completed on this
>> subject would be appreciated.  Thanks!
>>
>> Anthony Damico
>> Kaiser Family Foundation
>>
>>
>>
>> Here's a simple example of what I need done on a regular basis:
>>
>> #two numeric vectors
>> a <- c( 1 , NA , 7 , 2 , NA )
>>
>> b <- c( NA , NA , 9 , 1 , 6 )
>>
>> #this has lots of NAs
>> a > b
>>
>> #save this result in x
>> x <- (a > b)
>>
>> #overwrite NAs in x with falses (which we do a lot)
>> x <- ifelse( is.na( x ) , F , x )
>>
>> #now x has only trues and falses
>> x
>>
>>
>>
>> ################
>> Here's an example function that solves the problem for "greater than"
>> ################
>>
>>
>> #construct a function that performs the same steps:
>> "%>F%" <-
>>        function( a , b ){
>>
>>                x <- (a > b)
>>
>>                x.false <- ifelse( is.na( x ) , F , x )
>>
>>                x.false
>>
>>        }
>>
>> #run the function
>>
>> a %>F% b
>>
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