[R] Deleting columns from a matrix

dxc13 dxc13 at health.state.ny.us
Sun May 24 19:59:00 CEST 2009


Thanks, both of these methods work great!


Dimitris Rizopoulos-4 wrote:
> 
> one way is:
> 
> mat <- 
> matrix(c(rep(NA,10),1,2,3,4,5,6,7,8,9,10,10,9,8,NA,6,5,4,NA,2,1,rep(NA,10),1,2,3,4,NA,6,7,8,9,10), 
> 10, 5)
> ind <- colSums(is.na(mat)) != nrow(mat)
> mat[, ind]
> 
> 
> I hope it helps.
> 
> Best,
> Dimitris
> 
> 
> dxc13 wrote:
>> useR's,
>> I have a matrix given by the code:
>> mat <-
>> matrix(c(rep(NA,10),1,2,3,4,5,6,7,8,9,10,10,9,8,NA,6,5,4,NA,2,1,rep(NA,10),1,2,3,4,NA,6,7,8,9,10),10,5)
>> 
>> This is a 10x5 matrix containing missing values.  All columns except the
>> second contain missing values.  I want to delete all columns that contain
>> ALL missing values, and in this case, it would be the first and fourth
>> columns.  Any column that has at least one real number would remain. I
>> know
>> I can use "mat[,-1]" to delete the first column, but I have a much larger
>> matrix where it is impossible to tell how many columns contain all
>> missing
>> values and which don't.  
>> Is there a function or something else that may be able to help me
>> accomplish
>> this?
>> 
>> Thanks in advance.
>> dxc13 
> 
> -- 
> Dimitris Rizopoulos
> Assistant Professor
> Department of Biostatistics
> Erasmus University Medical Center
> 
> Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
> Tel: +31/(0)10/7043478
> Fax: +31/(0)10/7043014
> 
> ______________________________________________
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> and provide commented, minimal, self-contained, reproducible code.
> 
> 

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