[R] HOw to achieve big vector times big dataframe in R?

[Uwe Ligges]

On 14.03.2013 11:27, Jan van der Laan wrote:
>
> apply((t(as.matrix(b)) * a), 2, sum)


... where colSums(.) should be faster than apply(., 2, sum),
Uwe Ligges


> should do what you want.
>
> Why this works; see,
> http://cran.r-project.org/doc/manuals/r-release/R-intro.html#The-recycling-rule
> and the paragraph before that.
>
> Jan
>
>
>
> Tammy Ma <metal_licaling at live.com> schreef:
>
>> HI,
>>
>> I have the following question:
>>
>> Vector a with lenght 150
>>
>> A B C D.........
>>
>> dataframe b with dim 908X150
>>
>> 1   1   1   1.....
>> 2   2   2   2
>> 3   3   3   3
>> 4   4   4   4
>> ................
>>
>> final result I want is the vector with length 908:
>> A*1+B*1+C*1+D*1+.....
>> A*2+B*2+C*2+D*2+.....
>> A*3+B*3+C*3+D*3+.....
>> A*4+B*4+C*4+D*4+.....
>> ....
>>
>> because of too large dimension, how can I achieve this in R? Thanks.
>>
>> Kind Regards,
>> Tammy
>>
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
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>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> 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.