[R] By function

Liviu Andronic landronimirc at gmail.com
Sat Apr 9 17:33:34 CEST 2011


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:

> 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
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


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