Re: Function to calculate the geometric mean of an array

Hi, Dennis

Thank you very much for the function to to calculate the geometric mean. It works quite well, I also learn a lot of other functions and methods to do other calculations.

Thank you again for your kind help.


All my best!


Shawn




Wen.J.Qu
2012-10-14



·¢¼þÈË£º Dennis Shea
·¢ËÍʱ¼ä£º 2012-10-14 09:28:40
ÊÕ¼þÈË£º Wen.J.Qu@gmail.com
³­ËÍ£º ncl-talk
Ö÷Ì⣺ Re: [ncl-talk] Functions to calculate the arithmetic mean and geometricmean of an array?

No, NCL does not have a geometric mean function.

You can always write your own function.

---
undef ("geometric_mean")
function geometric_mean(x:numeric)
;
; Mathematical definition: The nth root of the product of n numbers.
; Practical definition: The average of the logarithmic values of a
data set,
; converted back to a base 10 number.
;
; The geometric mean applies only to positive numbers

local n, gmean
begin

   gmean = 0d0 ; force double
   if (isatt(x,"_FillValue") .and. all(ismissing(x)) ) then
       gmean = x@_FillValue
       return(gmean)
   end if

   if (any(x.le.0)) then ; numbers > 0 only
       gmean = getFillValue(x)
       return(gmean)
   end if

   n = num(.not.ismissing(x))
  ;n = product( dimsizes(x) )

   if (typeof(x).eq."double") then
       gmean = exp(avg(log(x)))
      ;gmean = product(x)^(1.d0/n)
   else
       gmean = exp(avg(log(x*1d0)))
      ;gmean = product(x*1d0)^(1.d0/n)
   end if

   gmean@opt = "geometric mean"
   return(gmean)
end


On 10/13/12 5:48 PM, Wen.J.Qu wrote:
> Hi, all
> Is there any functions to calculate the arithmetic mean and geometric
> mean of an array? I think the function "avg" seems can do the arithmetic
> mean. How about the geometric mean?
> Thanks a lot in advance.
> Shawn?
> ------------------------------------------------------------------------
> Wen.J.Qu
> 2012-10-13
>
>
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Received on Sun Oct 14 14:53:13 2012