Re: Filters

["Jennifer M. Adams" <miletta@xxxxxxxxxxxxxxxxxxx>]

> Is there a way to "high-pass" a time series with Ferret??

I recently spent a lot of time trying to use Ferret to do low and high
pass filtering of gridded data. It turned out to be rather complicated
script writing, even for the simplest case of a one-dimensional
timeseries, and too cumbersome to keep track of the various i's, j's, 
k's and t's of the original timeseries, the filtering weights, and the
filtered timeseries. I ended up doing it outside of Ferret in a C program,
using the library of netCDF routines to manipulate the data file. I read
in a two-dimensional piece of the original file, filtered it, and then
wrote it out to a new netCDF file. It ran extremely slowly, making me
suspect something was wrong with my brand new SUN Ultra 2 with two 
167 MHz processors. Perhaps there are other ferreters out there who 
have done it differently and/or more successfully...

Ilana, if you are interested in the C program I wrote, please write to me 
directly and I will forward it to you. 

Jennifer

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Jennifer Miletta Adams                          miletta@pmel.noaa.gov
Coastal and Arctic Research Division            (206)526-4532
NOAA Pacific Marine Environmental Laboratory
7600 Sand Point Way NE
Seattle, WA  98115-0070