**To**:**ferret_users@xxxxxxxxxxxxxxxxxxx****Subject**:**Re: axis points****From**:**Chris Weaver <weaver@xxxxxxxxxxxxxxxxxxxxxxxxxxx>**- Date: Tue, 22 Jun 1999 12:40:54 -0400 (EDT)
- Reply-to: Chris Weaver <weaver@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Sender: owner-ferret_users

Hi, Steve Hankin kindly provided me with some tools to determine what exactly happens when you perform certain types of regridding operations. Specifically, I wanted to know, when transforming an hourly data set to a daily-mean data set using regridding, what the "central time" of the average was and which particular hourly points went into each daily average. For example, if I define the following daily-mean axis: define axis/t="1-jul-1989:15:00:00":"31-jul-1989:15:00:00":1/units=days t1day let omega_daily = omega_hourly[gt=t1day@ave] I can find out more about what happened using the following (Steve's tools): LET ONE = omega_hourly*0 + 1 ! always one LET LINEAR = omega_hourly*0 + L ! linear in L let delta_pt = some-L-value LET DELTA = IF L EQ delta_point THEN 1 ! = 1 only at delta_point So, one[gt=t1day@sum] -- tells you how many points went into the average linear[gt=t1day@ave] -- tells you the center point of the averaging delta[gt=t1day@sum] -- tells you if the value at "delta_pt" is used in a calculation (You have to be careful about mixing world coordinates and simply numbered indices in the use of these tools to avoid incompatibilities using certain transformations.) I hope this might be helpful to some out there. Chris Weaver ------------------- C.P. Weaver Internet: Department of Environmental Sciences weaver@cep.rutgers.edu Rutgers University/Cook College www.envsci.rutgers.edu/~weaver 14 College Farm Road Phone: 1 732 932 7902 New Brunswick, NJ 08901-8551 Fax: 1 732 932 8644 USA

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