[R] By function

[Liviu Andronic]

Hello

On Fri, Apr 8, 2011 at 12:38 AM, Raoni Rodrigues
<caciquesamurai at gmail.com> wrote:
> Hello all!
>
> I have a data frame with nine variables and 293 cases. (attached goes
> the csv file).
>
The CSV didn't get through so it's difficult to replicate your
example. Please post the output of:
str(cpue)


> I need to calculate a index using the sum of one variable (N) divided
> by the length of other variable (Fisherman), but for each day (Date).
>
> I tried to use that codes:
>
> by (cpue, cpue$Date, function (x) sum (cpue$N)/length(cpue$Fisherman))
>
[..]

> In both codes, as result, I received the same value for all Date
> value. And, oddly, this result is the value of calculation for all
> data frame, as I used just:
>
> sum (cpue$N)/length(cpue$Fishermans)
>
>From the code above, this is expected since in the function()
statement you use the entire df (cpue) and not the subset (x). Try
this:
by (cpue, cpue$Date, function (x) sum (x$N)/length(x$Fisherman))


> Sorry for the basic question, but I worked on this simple code all day
> and can't do it work out! And have no idea why...
>
> I'm using R 2.11 in Windows XP.
>
It is often a good a idea to post the output of
sessionInfo()

Regards
Liviu



> Since now, thanks for the attention and all help,
>
> Best,
>
> Raoni
>
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> 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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