**Previous message:**MICHAEL NOTARO: "equiv_sample_size , ftest"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

Hello,

I see the problem. For the surface air temperature variable

data were available at all grid points. For SST there are some

grid points [ ~33% :-) ] that are all missing because they are

over land. The underlying fortran routine correctly set the internally

calculated lag-1 autocorrelation as missing (_FillValue). At this point

it should have returned with the equivalent sample size set to

_FillValue also. Unfortunaltely, it did not.

A fix will be applied in the near future.

Regards

Dennis Shea

*>Hi. I had a question about equivalent sample size and ftest.
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*>I created variables sst1(lat,lon,time) and sst2(lat,lon,time),
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*>and applied a low-pass filter to them. Then I calculated their
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*>variances. For land pts. I use the FillValue of 1e+35.
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*>Now, I want to determine if their variances are significantly
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*>different using the ftest. I included my approach below.
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*>However, the equiv_sample_size command leads to this error:
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*>
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*> ==>SLATEC/NCL: DGAMMA:
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*> ANSWER LT HALF PRECISION BECAUSE X TOO NEAR NEGATIVE INTEGER: NERR=
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[SNIP]

*>
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*>Previously, I did the same thing for surface air temperature without any
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errors.

*>Any idea what is wrong here? Thanks.
*

*>Mike
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*>
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*>**********************
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*>
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*> xEqv = equiv_
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*>sample_size (sst1, 0.1,0)
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*> yEqv = equiv_sample_size (sst2, 0.1,0)
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*> gwt = latGauWgt (128, "lat", "gaussian weights", "dimension_less ")
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*> xN = wgt_areaave (xEqv, gwt, 1., 0)
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*> yN = wgt_areaave (yEqv, gwt, 1., 0)
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*>
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*> alpha=new((/128,128/),float)
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*> alpha = 100.*(1. - ftest(var1,xN,var2,yN,0))
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*> alpha!0="lat"
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*> alpha!1="lon"
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*> alpha&lat=lat
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*> alpha&lon=lon
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*> alpha@_FillValue=1e+35
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*> alpha=mask(alpha,oro,0)
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*>
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*>
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*>_______________________________________________
*

*>ncl-talk mailing list
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*>ncl-talk AT ucar.edu
*

*>http://mailman.ucar.edu/mailman/listinfo/ncl-talk
*

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