PROCEDURE: thm_part_subtract PURPOSE: Subtracts from a particle distribution down to a minimum. (If units are in counts, you can use this to do 1 or N count subtraction) INPUTS: dist_data: A particle distribution array from thm_part_dist_array OUTPUTS: Replaces dat with a data structure with the requested counts subtract Keywords: error: Set to 1 on error, zero otherwise subtract_value: The amount to subtract(default: 1) minimum_value: The minimum after subtraction.(default 5e-3) Prevents asymptotes in moment calculations, negative values Example: dist_data = thm_part_dist_array(probe='a',type='peif',trange=['2012-02-08/09','2012-02-08/12']) ;load data(loaded in counts, by default) thm_part_subtract,dist_data ;subtract one count level thm_part_moments,inst='peif',probe='a',dist_array=dist_data ;calculate moments NOTES: Works with thm_part_dist_array.pro, see crib thm_crib_sst_extrapolation.pro, thm_crib_esa_extrapolation.pro for examples on new particle processing routines $LastChangedBy: pcruce $ $LastChangedDate: 2013-01-18 08:57:01 -0800 (Fri, 18 Jan 2013) $ $LastChangedRevision: 11462 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/themis/spacecraft/particles/thm_part_subtract.pro $