[R] more efficient sum of matrix columns

[Roger D. Peng]

colSums()/rowSums() will be *much* faster and you can specify na.rm = TRUE.

-roger

Jonathan Baron wrote:

>On 06/14/03 20:51, Jean Eid wrote:
>  
>
>>Dear R users,
>>I am looking for a more efficient way to compute the sum of columns of a
>>matrix.
>>I am currently using apply(data, 2, sum) however, I am building a data set
>>    
>>
>>from another one by summing the columns of some parts of the matrix.
>  
>
>>the loop is taking too long (about 1/2 hour) for a 4462 * 202 matrix.
>>    
>>
>
>colSums() might be faster, but I don't know how much faster.  It
>does not allow na.rm=T, but you don't have that, so it might
>help.
>
>--
>Jonathan Baron, Professor of Psychology, University of Pennsylvania
>R page:               http://finzi.psych.upenn.edu/
>
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>  
>