[R] column means dropping column minimum

[David L Carlson]

The which.min() only gets the first minimum value. If two or more values are tied for the minimum, it will delete only the first one. This would get them all:

> apply(test, 2, function(x) mean(x[-which(x == min(x))]))
   samp1    samp2    samp3 
66.66667 70.00000 73.33333

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Giorgio Garziano
Sent: Tuesday, December 8, 2015 12:58 PM
To: r-help at r-project.org
Subject: Re: [R] column means dropping column minimum

First, your code has flaws in the assignment of NA and in passing na.rm=TRUE to colMeans().

It should be:

test2 <- test
for (i in 1:ncol(test)) { test2[which.min(test[,i]),i]=NA}
print(test2)


samp1 samp2 samp3

1    60    60    NA

2    50    60    65

3    NA    90    65

4    90    NA    90



print(colMeans(test2,na.rm = TRUE))

   samp1    samp2    samp3

66.66667 70.00000 73.33333

For your purpose, I suggest the following:

apply(test, 2, function(x) { mean(x[-which.min(x)])})


GG



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