Hi everyone,
Ana sent me her data, with P and Q. These are variables that look
quite well correlated but with one being of larger magnitude than the
other. This is causing a loss of numeric accuracy; Ferret only operates
in singleprecision, and so the variations in the data of smaller
magnitude are overwhelmed by the larger numbers.
The result is improved with:
yes? use pq
yes? set var/name=q_in q ! I am going to redefine q
yes? let q = q_in/100
yes? go regresst
yes? stat rsquared
I'm asking some of our dataanalysis experts to chime in: What more
can we do to work with this data? I'm attaching the netCDF file.
yes? can data/all; use pq.nc
yes? stat p
VAR_1
LONGITUDE: 118.8E to 61.2W
LATITUDE: 36.2S to 16.2N
Z: N/A
TIME: 01JUN1958 00:00 to 01JUN2002 00:00
DATA SET: ./pq.nc
Total # of data points: 798336 (72*21*1*528)
# flagged as bad data: 0
Minimum value: 1000
Maximum value: 1031.3
Mean value: 1012.9 (unweighted average)
Standard deviation: 3.723
yes? stat q
VAR_2
LONGITUDE: 118.8E to 58.8W
LATITUDE: 36.2S to 16.2N
Z: N/A
TIME: 01JUN1958 00:00 to 01JUN2002 00:00
DATA SET: ./pq.nc
Total # of data points: 809424 (73*21*1*528)
# flagged as bad data: 0
Minimum value: 100000
Maximum value: 103278
Mean value: 101288 (unweighted average)
Standard deviation: 394.51
yes? set var/name=q_in q
yes? let q = q_in/100
yes? go regresst
...
yes? stat rsquare
(PQVAR*PQVAR) / (PVAR*QVAR)
LONGITUDE: 118.8E to 61.2W
LATITUDE: 36.2S to 16.2N
Z: N/A
TIME: 01JUN1958 00:00 to 01JUN2002 00:00
DATA SET: ./pq.nc
Total # of data points: 1512 (72*21*1*1)
# flagged as bad data: 0
Minimum value: 0.27778
Maximum value: 1.0833
Mean value: 0.8884 (unweighted average)
Standard deviation: 0.1003
Ana Redondo wrote:
Re: [ferret_users] Rsquare problem
Hi Ansley,
I am attaching you the file with the data
Thank you very much!!
Ana
On 20/10/09 10:30 AM, "Ansley Manke" <Ansley.B.Manke@xxxxxxxx> wrote:
Hi Ana,
Would it be possible for you to send me the data you are using? If you
do the following in Ferret, then you will produce a file that I should
be able to test this with:
yes? Let P=var_1
yes? Let Q=var_2
yes? save/file=pq.nc p,q
and then just attach the netcdf file to an email. This is not a large
amount of data, and these files email just fine. We can figure out
what's happening and then report back to the Ferret group.
I'm at the end of my day, and I see you're in Australia. This is always
the hard part about working with others around the world, but maybe
within another day we can get this figured out!
Ansley
Ana Redondo wrote:
Re: [ferret_users] Rsquare
problem Hi Ansley,
Yes the values of Rsquare are larger than 1:
yes? stat rsquare
Total # of data points: 1512 (72*21*1*1)
# flagged as bad data: 0
Minimum value: 0.34722
Maximum value: 1.2
Mean value: 0.89056 (unweighted average)
Standard deviation: 0.10312
Any ideas??
Thanks
Ana
On 20/10/09 2:16 AM, "Ansley Manke" <Ansley.B.Manke@xxxxxxxx> wrote:
Hi Ana,
Yes, the values of rsquare should be between 0 and 1. If you look at
the result of
yes?
STAT rsquare
are the values really larger than 1? I
wonder if the automatically chosen color fill levels in the FILL
command are making the color bar extend higher than 1 even though the
values of the data field are not actually larger than 1.
Another possibility is that the accuracy of numeric calculations is
putting values slightly larger than 1. Here too the STAT command might
tell us more.
Ansley
Ana Redondo wrote:
Rsquare problem Hi,
I am doing a linear regression between two independent variables in
order to find out the Rsquare. This is how I am doing it:
yes? Let P=var_1
yes? Let Q=var_2
yes? Go regresst
yes? show var
yes? fill rsquare
But when filling the Rsquare (and I also list some values to test) I
realized that some values are greater than 1!!!!!!!! Isn’t it Rsquare
the coefficient of determination? If so it should be 0<R^2<1,
what I am doing wrong???
Thanks
Ana
