On 28 Feb., 14:22, chris <rog...@googlemail.com> wrote:
> On 28 Feb., 13:13, Gray <grayliketheco...@gmail.com> wrote:
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>> On Feb 28, 6:43 am, chris <rog...@googlemail.com> wrote:
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>>> On 25 Feb., 16:25, Mark Shephard <mark.w.sheph...@gmail.com> wrote:
>
>>>> Hi,
>
>>>> I was wondering if anyone has anyone develope IDL routines for the
>>>> method of L-moments?
>
>>>> Thanks,
>>>> Mark
>
>>> Hi Mark,
>>> something like this?
>
>>> function cr_binomial,n,m
>>> n1=1d & m1=1d & n1m1=1d
>>> for i=1d,n do n1*=i
>>> for i=1d,m do m1*=i
>>> for i=1d,(n-m) do n1m1*=i
>>> return,n1/(m1*n1m1)
>>> end
>
>>> function cr_l_moment,dat
>>> n=n_elements(dat)
>>> l1 = total(dat,/double)/cr_binomial(n,1)
>>> l2=0d &l3=0d &l4=0d
>>> for i=1d,n do begin
>>> b1 = cr_binomial(i-1,1d)
>>> b2 = cr_binomial(n-i,1d)
>>> b3 = cr_binomial(i-1,2d)
>>> b4 = cr_binomial(n-i,2d)
>>> b5 = cr_binomial(i-1,3d)
>>> b6 = cr_binomial(n-i,3d)
>>> l2+=(b1-b2)*dat[i-1l]
>>> l3+=(b3-2*b1*b2+b4)*dat[i-1l]
>>> l4+=(b5-3*b3*b2+3*b1*b4+b6)*dat[i-1l]
>>> endfor
>>> l2*=0.5d /cr_binomial(n,2d )
>>> l3*=(1d / 3d )/cr_binomial(n,3d )
>>> l4*=(1d / 4d )/cr_binomial(n,4d )
>>> return,{l1:l2,l2:l2,l3:l3,l4:l4}
>>> end
>
>>> IDL> r=randomu(seed,5,5)
>>> IDL> inf=cr_l_moment(r)
>>> IDL> print,float(inf)
>>> { -0.000558181 -0.000558181 -0.0111168 0.212071}
>
>>> Cheers
>
>>> CR
>
>> I have no idea what L-moments are, but do you really need to use all
>> the FOR-loops?
>
>> function cr_binomial,n,m
>> n1 = product(dindgen(n)+1)
>> m1 = product(dindgen(m)+1)
>> n1m1 = product(dindgen(n-m)+1)
>> return, n1/(m1*n1m1)
>> end
>
> No, it is not necessary, so your suggestion reduces it to:
>
> function cr_l_moment,dat
> n=double(n_elements(dat))
> bin=product(dindgen(n)+1d,/c)
> l1 = total(dat)/bin[n-1l]
> l2=0. &l3=0. &l4=0.
> for i=1l,n do begin
> b1 = bin[i-1]
> b2 = bin[n-i]
> b3 = b1/2d
> b4 = b2/2d
> b5 = b1/6d
> b6 = b2/6d
> l2+=(b1-b2)*dat[i-1l]
> l3+=(b3-2*b1*b2+b4)*dat[i-1l]
> l4+=(b5-3*b3*b2+3*b1*b4+b6)*dat[i-1l]
> endfor
> l2*=bin[n-1]
> l3*=(1./3.)/(bin[n-1]/6d)
> l4*=(1./4.)/(bin[n-1]/24d)
> return,{l1:l2,l2:l2,l3:l3,l4:l4}
> end
>
> Cheers
>
> CR
The type of variables(double, long, float) is inconsistent. You have
to change this to double.
Cheers
CR
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