Thank you all. Really!
I have used the following function:

apply(dfrm, 1, function(x) mean(x[x>=0]) )

Someone of you even gave me a few interesting explanations
about why to use it.

Still thank you all.

Andrea

On Mon, May 14, 2012 at 6:52 PM, David Winsemius <dwinsemius@comcast.net>wrote:

>
> On May 14, 2012, at 12:32 PM, Andrea Sica wrote:
>
>  Dear all,
>>
>> I am sure it won't be difficult for you!!
>> I need to calculate the average among variables for the single units of my
>> dataset.
>> But, while doing it, I need to do not consider some values.
>> To better explain, think like there are two units and three variables:
>>
>>     V1    V2     V3
>> [1]   3     -2      4
>> [2]  -1      4      1
>>
>> and you want to calculate the average by row, without considering those
>> negative values:
>>
>> => mean(1row) = (3+4)/2
>> => mean(2row) = (4+1)/2
>>
>
> perhaps (untested in absence of reproducble example):
>
> apply(dfrm, 1, function(x) mean(x[x>=0]) ) # would also work for a matrix
> object.
>
>
>> Could anyone please give me the commands to do that in R?
>>
>> Thank you so much
>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________**________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
>> PLEASE do read the posting guide http://www.R-project.org/**
>> posting-guide.html <http://www.R-project.org/posting-guide.html>
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> David Winsemius, MD
> West Hartford, CT
>
>

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