[R] Why mean is not working in by?

[Dimitri Liakhovitski]

Sorry, I omitted the first line:

myvars <- c("Sepal.Length", "Sepal.Width")
by(data = iris[myvars], INDICES = iris["Species"], FUN = summary)
by(data = iris[myvars], INDICES = iris["Species"], FUN = sum)
by(data = iris[myvars], INDICES = iris["Species"], FUN = var)
by(data = iris[myvars], INDICES = iris["Species"], FUN = max)
by(data = iris[myvars], INDICES = iris["Species"], FUN = min)

by(data = iris[myvars], INDICES = iris["Species"], FUN = sd)
by(data = iris[myvars], INDICES = iris["Species"], FUN = mean)

The first lines are doing what I expected them to do: for each level
of the factor "Species" they gave me a summary, a sum, a variance, a
max, a min for each of the 2 variables in question (myvars).
I expected by to generate the sd and the mean for the 2 variables in
question for each level of "Species".

On Tue, Dec 8, 2015 at 5:50 PM, Sarah Goslee <sarah.goslee at gmail.com> wrote:
> Hi Dimitri,
>
> I changed this into a reproducible example (we don't know what myvars
> is). Assuming length(myvars) > 1, I'm not convinced that your first
> five lines "work" either: what do you expect?
>
> I get:
>
>> by(data = iris[, -5], INDICES = iris["Species"], FUN = min)
> Species: setosa
> [1] 0.1
> ------------------------------------------------------------------
> Species: versicolor
> [1] 1
> ------------------------------------------------------------------
> Species: virginica
> [1] 1.4
>
> But was expecting:
>
>> aggregate(iris[,-5], by=iris[,"Species", drop=FALSE], FUN=min)
>      Species Sepal.Length Sepal.Width Petal.Length Petal.Width
> 1     setosa          4.3         2.3          1.0         0.1
> 2 versicolor          4.9         2.0          3.0         1.0
> 3  virginica          4.9         2.2          4.5         1.4
>
>
>
> aggregate(iris[,-5], by=iris[,"Species", drop=FALSE], FUN=sd)
> aggregate(iris[,-5], by=iris[,"Species", drop=FALSE], FUN=mean)
>
> provide the answers I would expect. If you want clearer advice, you
> need to provide an actually reproducible example, and tell us more
> about what you expect to get.
>
> Sarah
>
>
> On Tue, Dec 8, 2015 at 5:30 PM, Dimitri Liakhovitski
> <dimitri.liakhovitski at gmail.com> wrote:
>> Hello!
>> Could you please explain why the first 5 lines work but the last 2 lines don't?
>> Thank you!
>>
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = summary)
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = sum)
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = var)
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = max)
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = min)
>>
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = sd)
>> by(data = iris[myvars], INDICES = iris["Species"], FUN = mean)
>>
>> --
>> Dimitri Liakhovitski
>>



-- 
Dimitri Liakhovitski