[R] Odp: Apply function

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 11.11.2008 06:59:55:

> 
> Hi all
> 
> I am manipulating a datafram which has 3 variables.Such as:
> 
> 1  2  3
> 4  5  6
> . 
> .
> .
> 200  210  300
> 
> I also has a row index: index=c(100,200,250..300)
> I want to find the sums of first 100 rows, then the sum from row 101 to 
row
> 200, then row 201 to row 250... the each end row is indicated by the 
index.

A little bit vague question, hence vague answer.

make a factor which has 3 values repeated 100 times (rep) and then use 
almost any of aggregation function ( e.g. tapply, by, aggregate) with sum 
function.

Regards
Petr

> 
> Can I use the apply function to do that? or any other way?
> 
> Thanks
> 
> Ted
> 
> 
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