[R] ignoring zeros or converting to NA

[stephen sefick]

I have been reading this thread and I am having a hard interpreting
what these mean.  I know that the result is that all of the values
that are zero in a are replaced by NA.  Let me try and write it out

is.na(a[a==0] ) <- TRUE
you pull out of a all of the times that are equal to zero then is.na
tests and returns false then all of the false values are set to true?

is.na(a) <- a==0
make values in a NA  when a is 0?

is this right?  what the logic if not?
thanks

Stephen Sefick


On Tue, Aug 12, 2008 at 6:32 PM, Charles C. Berry <cberry at tajo.ucsd.edu> wrote:
> On Tue, 12 Aug 2008, Mike Prager wrote:
>
>> rcoder <mpdotbook at gmail.com> wrote:
>>
>>> I have a matrix that has a combination of zeros and NAs. When I perform
>>> certain calculations on the matrix, the zeros generate "Inf" values. Is
>>> there a way to either convert the zeros in the matrix to NAs, or only
>>> perform the calculations if not zero (i.e. like using something similar
>>> to
>>> an !all(is.na() construct)?
>>
>> Is this what you are looking for?
>>
>>> # make some data
>>> a = matrix(c(rep(0,6), rep(2,6)), nrow = 4)
>>> a
>>
>>    [,1] [,2] [,3]
>> [1,]    0    0    2
>> [2,]    0    0    2
>> [3,]    0    2    2
>> [4,]    0    2    2
>>>
>>> # change zero to NA
>>> is.na(a[a==0] ) <- TRUE
>
> Or
>        is.na(a) <- a==0
>
> Chuck
>
>>> a
>>
>>    [,1] [,2] [,3]
>> [1,]   NA   NA    2
>> [2,]   NA   NA    2
>> [3,]   NA    2    2
>> [4,]   NA    2    2
>>
>> --
>> Mike Prager, NOAA, Beaufort, NC
>> * Opinions expressed are personal and not represented otherwise.
>> * Any use of tradenames does not constitute a NOAA endorsement.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> Charles C. Berry                            (858) 534-2098
>                                            Dept of Family/Preventive
> Medicine
> E mailto:cberry at tajo.ucsd.edu               UC San Diego
> http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



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