[R] calculating median with a condition

[Chuck Cleland]

On 7/20/2009 2:59 PM, 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)])}
> 
>  
> 
> Can someone suggest me the correct R script to do what I have explained
> above.

X <- as.data.frame(matrix(rnorm(100), ncol=10))

apply(X, 1, function(x){median(x[x > 0])})

 [1] 0.2297943 0.6476565 0.4699609 0.8744830
 [5] 1.0242502 0.7800703 0.6648436 0.2930191
 [9] 0.6001506 1.0767194

> Thanks
> 
> Manisha
> 
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> 
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-- 
Chuck Cleland, Ph.D.
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