[R] how to find the mean and sd :(

[Bert Gunter]

?tapply

or better yet

?ave ## a wrapper for tapply

allows it to be done without extraction.

Cheers,

Bert


Bert Gunter

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
   -- Clifford Stoll


On Fri, Sep 11, 2015 at 9:02 AM, Tom Wright <tom at maladmin.com> wrote:
> On Fri, 2015-09-11 at 07:48 -0700, massmatics wrote:
>> AM.warpbreaks<=30
>
> The above command is not returning what you expected, what part of the
> AM.warpbreaks dataframe is expected to be <= 30?
>
> Effectively you are using a two stage process.
> 1) Create a logical vector identifying rows in the dataframe with a
> breaks value <= 30
> 2) use the vector in 1. to extract just the rows you are interested in
> and use that to calculate the mean of the breaks column.
>
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