[R] mean for every quartile

[Michael Dewey]

Dear Elahe

In line

On 16/05/2016 13:31, ch.elahe via R-help wrote:
> Hi all,
> I have a column in my df and I want to get quartiles for this column and then calculate mean for each and every quartile, here is my column:
>

The quartiles are strictly speaking the boundaries but if you really 
meant that the problem is trivial so i assume you want to cut the 
variable at the quartiles.

>
>     df$BR
>     [1] 384 384 384 384 512 384 384 320 320 320 320 320 320 320 320 320 320 384
>     [19] 384 384 320 320 320 320 384 384 256 320 320 320 384 320 320 320 384 384
>     [37] 320 320 320 320 320 320 320 320 320 384 320 320 320 320 320 320 384 320
>     [55] 320 320 320 320 320 320 384 512 320 320 320 320 320 320 320 384 384 320
>     [73] 320 320 384 320 320 320 320 256 320 320 384 320 384 320 384 320 320 320
>     [91] 384 320 320 320 320 320 320 320 320 320 320 320
>
> I do the following to get the quartiles:
>
>
>     quantile(m$BR)
>     0%  25%  50%  75% 100%
>     256  320  320  368  512
>
> now how can I get mean for each quartile?

How about setting up a vector which takes the values 1, 2, 3, 4 
depending on the values of BR with cutpoints defined by 
quantile(BR)(using ifelse) and then using tapply?

> Thnaks for any help,
> Elahe
>
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html