Thanks.
Why can't the MAD just be implemented as `mad(x) = median(abs(x -
median(x)))` ?
Cheers,
Daniel.
On 27 July 2016 at 15:49, j verzani <jverz...@gmail.com> wrote:
> It seems `mad` calls `mad!` with a copy. The mad! function reuses the
> copied vector for storage. As the differences from the median are not
> integers you get an assignment error. That's fussy and should be easily
> addressed. The multiplier is also done by default in R so that the units of
> spread for mad and sd are similar.
>
> On Wednesday, July 27, 2016 at 5:50:02 AM UTC-4, Daniel Carrera wrote:
>>
>> Hello,
>>
>> My "mad" function seems to be broken. Maybe I just don't know how to use
>> it right:
>>
>> julia> using StatsBase
>>
>> julia> @doc mad
>> No documentation found.
>>
>> StatsBase.mad is a generic Function.
>>
>> # 2 methods for generic function "mad":
>> mad{T<:Real}(v::Range{T<:Real}, args...) at
>> /home/daniel/.julia/v0.4/StatsBase/src/scalarstats.jl:180
>> mad{T<:Real}(v::AbstractArray{T<:Real,N}, args...) at
>> /home/daniel/.julia/v0.4/StatsBase/src/scalarstats.jl:179
>>
>> julia> mad([1,2,3,4])
>> ERROR: InexactError()
>> in mad! at /home/daniel/.julia/v0.4/StatsBase/src/scalarstats.jl:184
>> in mad! at /home/daniel/.julia/v0.4/StatsBase/src/scalarstats.jl:183
>> in mad at /home/daniel/.julia/v0.4/StatsBase/src/scalarstats.jl:179
>>
>> julia>
>>
>>
>>
>> Does anyone know what's happening? Also, I am confused by the "constant"
>> parameter. The documentation says:
>>
>> mad(*x*[, *center][; constant=1.4826*])
>> <http://statsbasejl.readthedocs.io/en/latest/scalarstats.html#mad>
>>
>> Compute the median absolute deviation
>> <http://en.wikipedia.org/wiki/Median_absolute_deviation> of x.
>>
>> One can optionally supply the center. By default, constant=1.4826 for
>> consistent estimation of the standard deviation of a normal distribution.
>>
>>
>>
>> Does this mean that, by default, the mad() function doesn't give you the
>> MAD, bunt instead it gives you MAD*1.4826 ?
>>
>> Thanks for the help.
>>
>> Cheers,
>> Daniel.
>>
>>
>>
>>
>> --
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