From: gibies george <gibies_at_nyahnyahspammersnyahnyah>

Date: Sun Mar 13 2011 - 22:01:24 MDT

Date: Sun Mar 13 2011 - 22:01:24 MDT

On 14 March 2011 02:01, John Kerfoot <johnkerfoot@gmail.com> wrote:

*> I've got a large AVHRR sea-surface temperature dataset for which I'm
*

*> trying to mask out some bad values; however I'm seeing some strange
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*> (and contradictory) behavior when using the mask function and I'm
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*> looking for some clarification.
*

*>
*

*> Before getting to the AVHRR dataset, I tried the following to make
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*> sure that I understood how mask worked:
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*>
*

*> ; Array to mask
*

*> x = ispan(0,8,1);
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*> print(x);
*

*>
*

*> ; Mask values
*

*> f = (/1, 1, 1, 2, 2, 2, 3, 3, 3/);
*

*> print(f)
*

*>
*

*> : Mask all corresponding values in x where f is less than 3
*

*> z = mask(x, (f.lt.3), True);
*

*>
*

Here the function have Masked all corresponding values in x *except where f

is less than 3*

*

*

*> print(z);
*

*>
*

*> I expected the first 6 values of x to be set to the fill value, but
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*> the opposite happened:
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*>
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*> Variable: x
*

*> Type: integer
*

*> Total Size: 36 bytes
*

*> 9 values
*

*> Number of Dimensions: 1
*

*> Dimensions and sizes: [9]
*

*> Coordinates:
*

*> (0) 0
*

*> (1) 1
*

*> (2) 2
*

*> (3) 3
*

*> (4) 4
*

*> (5) 5
*

*> (6) 6
*

*> (7) 7
*

*> (8) 8
*

*>
*

*>
*

*> Variable: f
*

*> Type: integer
*

*> Total Size: 36 bytes
*

*> 9 values
*

*> Number of Dimensions: 1
*

*> Dimensions and sizes: [9]
*

*> Coordinates:
*

*> (0) 1
*

*> (1) 1
*

*> (2) 1
*

*> (3) 2
*

*> (4) 2
*

*> (5) 2
*

*> (6) 3
*

*> (7) 3
*

*> (8) 3
*

*>
*

*>
*

Here the function have Masked all corresponding values in x *except where f

is less than 3*

*

*

*>
*

*> Variable: z
*

*> Type: integer
*

*> Total Size: 36 bytes
*

*> 9 values
*

*> Number of Dimensions: 1
*

*> Dimensions and sizes: [9]
*

*> Coordinates:
*

*> Number Of Attributes: 1
*

*> _FillValue : -999
*

*> (0) 0
*

*> (1) 1
*

*> (2) 2
*

*> (3) 3
*

*> (4) 4
*

*> (5) 5
*

*> (6) -999
*

*> (7) -999
*

*> (8) -999
*

*>
*

*>
*

*>
*

*> So I'm clearly not understanding how to use this function. Can
*

*> someone explain this result? How can I get all values of x to be
*

*> masked where f is less than 3?
*

*>
*

*> Once I understand this, I'll have a follow up question using the AVHRR
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*> datset.
*

*>
*

*> thanks in advance,
*

*> John
*

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*

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*

*>
*

-- *Gibies George, CSIR-RF,* *Seasonal Scale Prediction Group, Climate and Global Modelling Division, Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, NCL (P. O.), Pashan, Pune 411008, India.* *http://sites.google.com/site/gibiesge/* Please Think about the environment. Save paper; Save Trees; and don't print this e-mail unless it is necessary.

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Received on Sun Mar 13 22:01:31 2011

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