[R] calculating median with a condition

[James W. MacDonald]

Hi Manisha,

Manisha Brahmachary wrote:
> Hello,
> 
>  
> 
> I am trying to calculate the median of numbers across each row for the data
> shown below  , with the condition that if the number is negative, that it
> should be ignored and the median should be taken of only the positive
> numbers.
> 
>  
> 
> For eg: data is in Column A,B,C. Column D and E demonstrates what I want to
> get as answer
> 
>  
> 
> A
> 
> B
> 
> C
> 
> Median
> 
> median value
> 
> -13.6688115
> 
> -32.50914055
> 
> -50.54011892
> 
> all negative, so ignore
> 
>  NA
> 
> NA
> 
> -53.65656268
> 
> 42.58599666
> 
> median C
> 
> 42.58599666
> 
> 33.30683089
> 
> 18.93765489
> 
> -25.17024229
> 
> median A,B
> 
> 26.12224289
> 
>  
> 
> The R script I have written is below( which  doesnot  do the job properly)
> 
>  
> 
> median.value<- matrix(nrow=nrow(data),ncol=1)
> 
> for(k in 1:nrow(data)){
> 
> median.value[k]<-median(data[which(data[k,]>0)])}

meds <- apply(data, 1, function(x) ifelse(median(x) < 0, median(x[x >= 
0]), median(x)))

I would normally avoid variable names like data, as you are masking a 
function by the same name.

Best,

Jim


> 
>  
> 
> Can someone suggest me the correct R script to do what I have explained
> above.
> 
>  
> 
> Thanks
> 
> Manisha
> 
>  
> 
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
James W. MacDonald, M.S.
Biostatistician
Douglas Lab
University of Michigan
Department of Human Genetics
5912 Buhl
1241 E. Catherine St.
Ann Arbor MI 48109-5618
734-615-7826