[R] sum(..., na.rm=TRUE) oddity

[rohan sadler]

Okay,

This is one of the cases where I can answer my own foolishness. If I 
don't define the switch as na.rm=TRUE, but instead just as TRUE - which 
is my usual practice with other functions - then sum counts the TRUE as 
another vector object, and counts it as one. So much for saving keystrokes.

rohan sadler wrote:

> Hi all,
>
> I get two different results when using sum() and the switch na.rm. The 
> result is correct when na.rm=FALSE.
> Linux Redhat 7.3, R version 1.6.1.
>
> I've had no luck searching the mail archives, so I was hoping somebody 
> could explain/check this one for me. I will need to apply the function 
> to missing data, simple as it is.
>
> Code:
>
> x<-matrix(runif(20,0,5)%/%1,4,5) # random matrix data set 4x5, values 
> are integers between 0 and 4
>
> coords<-c(2,3,3,4) # choose any sub-matrix, with 
> c(ymin,ymax,xmin,xmax) being row and column indices.
>
> occupied.counter<-function(coords){sum(x[coords[3]:coords[4],coords[1]:coords[2]])} 
>
>
> occupied.counter(coords)
> [1] 7
>
> occupied.counter<-function(coords){sum(x[coords[3]:coords[4],coords[1]:coords[2]], 
> na.rm=TRUE)}
>
> occupied.counter(coords)
> [1] 8
>
>
> Cheers in advance
>
> Rohan Sadler
>

-- 
PhD Student, Ecosystems Research Group (ERGO)
School of Plant Biology (Botany), Faculty of Natural & Agricultural Sciences,
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