PARTICLE_TRACK_2D - track the movement of one or more particles using a second order finite difference approach (Bennett and Clites, 1987). Usage: [t, lon, lat] = particle_track_2nd( hfrc_obj, start_t, end_t, ... coords, max_dist, ... ) This function moves particles along with the currents. It uses the 2nd order algorithm of Bennett and Clites (1987) with a variable time step that is determined so that no particle moves more than max_dist per time step. It assumes that velocities are in cm/s. hfrc_obj will be temporally sorted before tracking is done. coords is a 2 column array of longitudes and latitudes of the particles to be tracked. If absent, hfrc.totalGrid is used. max_dist specifies what is the maximum distance to move in a time step. If absent, 0.25 kms is used. start_t and end_t are the start and end times of the tracking. If absent, the entire time series will be used. start_t and end_t should be in matlab units. This routine will end before end_t if all particles have gone out of data region (produced NaN). Nothing is done to bad data in this routine. 0's will be treated like zeros, NaNs like NaNs. The final ... represents extra arguments to griddata, such as 'method', to be used when interpolating values. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% $Id: particle_track_2nd.m,v 1.5 2004-11-11 20:29:56 dmk Exp $ Copyright (C) 2003 David M. Kaplan Licence: GPL %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

- diff DIFF - This function tries to differentiate the variables in
- end END - basic end method for HFRC objects.
- griddata GRIDDATA - Grid and interpolate spatial data.
- isnan ISNAN - returns position of any NaN data in either U or V.
- km2lonlat KM2LONLAT - Converts dimensions of totalGrid from kms to lon,lat
- length LENGTH - returns number of times in HFRC object.
- lonlat2km LONLAT2KM - Converts dimensions of totalGrid to kms from lon,lat
- mean MEAN - mean of a field in an HFRC object
- size SIZE - returns [ (num times), (num gridpts) ].
- sortT SORTT - this function sorts data rows of an HFRC object in order of
- subsref SUBSREF Get HFRC elements easily

- reverse_particle_track_2nd REVERSE_PARTICLE_TRACK_2ND - uses particle_track_2nd in reverse to find

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