Hi. I had a question about equivalent sample size and ftest.
I created variables sst1(lat,lon,time) and sst2(lat,lon,time),
and applied a low-pass filter to them. Then I calculated their
variances. For land pts. I use the FillValue of 1e+35.
Now, I want to determine if their variances are significantly
different using the ftest. I included my approach below.
However, the equiv_sample_size command leads to this error:
ANSWER LT HALF PRECISION BECAUSE X TOO NEAR NEGATIVE INTEGER: NERR=
1: LEVEL= 1
==>SLATEC/NCL: DBETAI: P AND/OR Q IS LE ZERO: NERR= 2: LEVEL=
==>SLATEC/NCL: DLBETA: BOTH ARGUMENTS MUST BE GT ZERO: NERR= 1
: LEVEL= 2
==>SLATEC/NCL: DGAMMA: X IS A NEGATIVE INTEGER: NERR= 4: LEVEL=
Previously, I did the same thing for surface air temperature without any errors.
Any idea what is wrong here? Thanks.
xEqv = equiv_
sample_size (sst1, 0.1,0)
yEqv = equiv_sample_size (sst2, 0.1,0)
gwt = latGauWgt (128, "lat", "gaussian weights", "dimension_less ")
xN = wgt_areaave (xEqv, gwt, 1., 0)
yN = wgt_areaave (yEqv, gwt, 1., 0)
alpha = 100.*(1. - ftest(var1,xN,var2,yN,0))
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