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matrix multiplication [message #91808]

Sun, 30 August 2015 11:04

siumtesfai
Messages: 62
Registered: April 2013

Member

Hi all

I have two dimensional data (2Ddata) with missing value ( NAN).

sz=size(2Ddata)

How can I calculate matrix multiplication by excluding the missing data

matrix = (1/ntime-1) * (Double(2Ddata) ## Transpose(2Ddata))

Best regards

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Re: matrix multiplication [message #91841 is a reply to message #91808]

Thu, 03 September 2015 10:02

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On Sunday, August 30, 2015 at 1:04:04 PM UTC-5, siumt...@gmail.com wrote:
> Hi all
>
> I have two dimensional data (2Ddata) with missing value ( NAN).
>
> sz=size(2Ddata)
>
>
>
> How can I calculate matrix multiplication by excluding the missing data
>
>
> matrix = (1/ntime-1) * (Double(2Ddata) ## Transpose(2Ddata))
>
>
> Best regards

What are you expecting to happen where the missing data are? It's not well-defined what a missing value times a non-missing value is -- IDL will give you NaN there, which is the only sensible answer I can see. If you're expecting something else, what fundamentally do you expect there?

-Jeremy.

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