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

[Tom Wright]

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.