[R] how to ignore NA when using cumsum?

[Ista Zahn]

Hi Tracy,
What do you want the program to do with the missing values? If you
want to treat them as zeros, you could use

cum.na <- function(x) {
x[which(is.na(x))] <- 0
return(cumsum(x))
}
cumsums <- apply(proportion, 1, cum.na)

-Ista

On Sat, Nov 21, 2009 at 2:34 PM, Tracy Bowerman
<tracy.bowerman at aggiemail.usu.edu> wrote:
> I would like to cumulatively sum rows in a matrix, in which each row has 1
> NA value.  The usual "na.rm=TRUE" does not seem to work with the command
> cumsum.  Is there another way to ignore the NAs or do I need to figure out a
> different way to do this?
>
> Here's an example matrix of title "proportion":
>
>        Ntrail    Strail      NFJD     Baldy     Onion      Crane
> [1,]        NA 0.2944937 0.1779969 0.1808015 0.2296511 0.11705683
> [2,] 0.2882713        NA 0.1795668 0.1823961 0.2316766 0.11808925
> [3,] 0.1716890 0.1769419        NA 0.3518116 0.2025204 0.09703714
> [4,] 0.1726311 0.1779128 0.3482548        NA 0.2036317 0.09756961
> [5,] 0.2252904 0.2321833 0.2059743 0.2092197        NA 0.12733223
> [6,] 0.2052614 0.2115415 0.1764081 0.1791877 0.2276013         NA
>
> I want cumulative sums for each row.
> Here's the code that works until it reaches an NA, then returns all
> subsequent values as NA.  Adding na.rm=TRUE returns the error:
> Error in FUN(newX[, i], ...) :  2 arguments passed to 'cumsum' which
> requires 1
>
> cumsums <- apply(proportion, 1, cumsum)
>
> Thank you,
> Tracy
>
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-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org