;+ ;Procedure: ; thm_part_slice2d_smooth ; ; ;Purpose: ; Helper function for thm_part_slice2d. ; Smooths the output data by applying a gaussian blur. ; ; ;Input: ; part_slice: (float) N x N array containing the slice data ; width: (int) width of smoothing window in points in both x and y ; ; ;Output: ; None, modifies part_slice. ; ; ;Notes: ; ; ; ;$LastChangedBy: aaflores $ ;$LastChangedDate: 2013-10-30 17:31:16 -0700 (Wed, 30 Oct 2013) $ ;$LastChangedRevision: 13454 $ ;$URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/themis/spacecraft/particles/slices/thm_part_slice2d_smooth.pro $ ; ;- ; Smooths slice output using a 2D gaussian convolution. ; Smoothing window should be an odd # of points >= 3 ; pro thm_part_slice2d_smooth, part_slice, width compile_opt idl2, hidden smooth = round(width) if smooth ge 2 then begin ;ensure kernel with odd # of elements in [3:slice resolution] n = smooth > 3. < dimen1(part_slice) if n mod 2 eq 0 then n-- ;Increase the STDV with the smoothing width to allow CONVOL to ;effectively smooth over a greater area. Simply extending the ;width with constant STDV adds negligable terms to the kernel. ;Allowing the STDV to grow too quickly results in flat distributions. c = alog(n) - .25 ;There's no simple solution for c = f(n) for small n ;so this was partly arrived at empirically. It ;should allow the width of the gaussian to increase ;with the smoothing window without becoming flat ;(too quick) or adding negligible terms (to slow). ;set up for kernel s = findgen(n) - floor(n/2.) sx = s ## replicate(1.,n) sy = s # replicate(1.,n) ;2D normalized gaussian kernel kernel = exp( (-.5) * ((sx/c)^2 + (sy/c)^2) ) ;/ (2*!pi*c^2) kernel = kernel / total(kernel) part_slice = convol(part_slice, kernel, /edge_zero) ; part_slice = smooth(part_slice, smooth) ; negidx = where(part_slice lt 0, nneg) ; if nneg gt 0 then begin ; part_slice[negidx] = 0 ; endif endif else begin dprint, dlevel=1, 'Smoothing not applied. Smoothing value must be >= 2' endelse return end