DIFF - This function tries to differentiate the variables in the HFRC object. Usage: deriv = diff( hfrc_obj, hfrc_var_name, 't' ) deriv = diff( hfrc_obj, hfrc_var_name, 'x' or 'y', 'griddata', ...) deriv = diff( hfrc_obj, hfrc_var_name, 'x' or 'y', dim ) [deriv,num] = diff( ... ) hfrc_var_name specifies the name of the variable you wish to differentiate. It should be something like 'U', 'V', 'NumRadials{1}', 'covariance', 'gridflag', 'U_error' or 'V_error'. The third argument specifies the dimension along which the differentiation will take place. If the fourth argument is 'griddata' (the default), then HFRC/griddata is used to approximate the function at nearby points and these values are used to calculate the derivative. If the fourth argument is of class "double", then data is assumed to be on a regular NS/EW grid , and dim should be a two element vector with the dimensions of the grid (as produced by meshgrid). Derivatives are calculated using central differences so that the result has the same number of elements as the original. If one side produces an NaN, then the other side will be used alone. ... represents extra arguments to be passed directly to HFRC/griddata. The results are always returned with appropriate units: (..)/kms or (..)/day, depending on the variable being differentiated by. Note that this means that if U & V have units of cm/s, then the result of dU/dx will have units cm/s/km. No attempt is made to put the variable in more obvious units. If a second output argument is requested, then this argument will contain a matrix the size of the derivative with the number of good derivatives used - for example, if both sides of the derivative were good at a point and time, then the result will be 2; if one side was good and the other was bad (NaN), then the result will be 1 ... %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% $Id: diff.m,v 1.12 2003-06-14 03:07:59 dmk Exp $ Copyright (C) 2001 David M. Kaplan Licence: GPL %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

- diff DIFF - This function tries to differentiate the variables in
- end END - basic end method for HFRC objects.
- gooddata GOODDATA - returns a matrix of good data in object.
- griddata GRIDDATA - Grid and interpolate spatial data.
- isempty
- 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) ].
- dist DIST - computes distance in between points in euclidean space.

- axis AXIS - sets figure axis scaling according to HFRC object.
- diff DIFF - This function tries to differentiate the variables in
- fft FFT - fft transforms a HFRC object
- get Gets HFRC elements.
- gradcrossUV GRADCROSSUV - computes dU/dx - dV/dy
- graddotUV GRADDOTUV - computes dU/dx + dV/dy
- ifft IFFT - ifft transforms a HFRC object
- particle_track PARTICLE_TRACK - track the movement of one or more particles.
- particle_track_2nd PARTICLE_TRACK_2D - track the movement of one or more particles using a
- particle_track_2nd_largeGrid PARTICLE_TRACK_2D_LARGEGRID - track the movement of one or more particles
- EOF EOF - computes EOF of a matrix.
- distance_bar Usage: [bar_handle, text_handle, location] = distance_bar( distance, location )
- isinpoly ISIN = ISINPOLY(X,Y,XP,YP) Finds whether points with
- perimetr PERIMETER Perimeter (length) of a polygon.
- velocity_arrow Usage: [arrow_handle, text_handle, location] = velocity_arrow( velocity, scale, units, location )

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