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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