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--- internal:administration:idl [2025/11/27 11:56] – [general structure] jan
+++ internal:administration:idl [2026/04/28 08:26] (current) – [interpolation] jan
@@ Line 626: / Line 626: @@
   * As matrix operations are faster than for-loops this may speed up your code a lot ...
+  * Alternatively one may use **rebin** , but note that rebin uses bilinear interpolation (sample=0) or nearest neigbor (sample=1) and accordingly might be a bit slower
+  x = fltarr(Nx)
+  y = fltarr(Ny)
+  xx = rebin( x, Nx, Ny, sample=1 )
+  yy = transpose(rebin( y, Ny, Nx ))
 ==== procedure names ====
@@ Line 815: / Line 823: @@
   ss[0] = 'wind speed'
   ss[1] = 'm/s'
+An array of strings can be also be splitted element by element, but only from Idl version 8. onwards.
+The result will be a  [[https://www.nv5geospatialsoftware.com/docs/list.html|LIST-Object]] , which might be converted to an array by using its method [[https://www.nv5geospatialsoftware.com/docs/list.html#ToArrayMethod|List::toArray()]] (note the brackets!).
+  s = [ 'a=b', 'c=d', 'e=f' ]
+  sL = STRSPLIT( s, '=', /ex, count=N )
+  sA = (STRSPLIT( s, '=', /ex, count=N )).toArray(  ) ; equal to sA = sL.toArray()
+Result %%sL%% will be a %%LIST%% object with N elements, and every entry of sL an array of strings with elements accorrding to the result fo strsplit.
+Parameter %%N%% will be an array with the number of splits that could be made per element.
+The conversion %%sL.toArray()%% works only if every entry in sL has the same number of elements.
+The %%sA%% array would allow you to search for certain values in the array by using the where functions - eg:
+  ia = where( sA[*,0] eq 'a', Na )
+But you could also try to use the %%WHERE%% method of the %%LIST%% object ...
@@ Line 821: / Line 846: @@
-filenames can be separated into path and name by
+filenames can be separated into path and name with
-  file_dirname( <path to file> )
+  f_dn = file_dirname( <path to file> )
-  file_basename( <path to file> )
+  f_bn = file_basename( <path to file> )
+where the dirname will have no '/' charcater.
+You may use strsplit to strip or get the 'filename extension' - the part of the filename after the last dot:
+  f_ext = (STRSPLIT( f_bn, '.', /ex, count=N ))[N-1]
+  f_bnx = STRJOIN((STRSPLIT( f_bn, '.', /ex, count=N ))[0:N-2],'.')
 ==== formatted output ====
@@ Line 1769: / Line 1801: @@
     xrange = [ 0.5 * hour, 2*1e6 ], $
     /xlog, $
-    xticks = N_ticks-1, $  ; holy IDL - why do you need things like this ?
+    xticks = N_ticks-1, $  ; xticks is the number of //intervals// not ticks!,  holy IDL - why do you need things like this ?
     xtickname = x_tiknams, $
     xtickv    = x_tikvals, $
@@ Line 3071: / Line 3103: @@
   extrm_lev_max = +(machar()).xmax
-See function [[https://www.harrisgeospatial.com/docs/machar.html|function machar]].
+See function [[https://www.nv5geospatialsoftware.com/docs/MACHAR.html|function machar]].
@@ Line 3087: / Line 3119: @@
     /overplot
-Keyword c_annotations is used here toprovide a format - this is usually not necessary.
+Keyword c_annotations is used here to provide a format - this is usually not necessary.
 You can define also different thicknesses, colors etc. with the other %%c_...%% key words of %%contour%%
 see [[http://www.physics.nyu.edu/grierlab/idl_html_help/C40.html#wp908085| help for contour]].
+=== line patterns ===
+contour can draw hatch patterns - but note: the pattern is not transparent.
+  contour, z, x, y, $
+    levels = levels, $
+    c_orientation = [ 0 , 22, 45, 90, ... ] , $ ; orientation of the lines in degrees
+    c_spacing = [ 1, 0.5, 0.25, ... ] ; spacing between lines in cm
+=== Path of contour lines ===
+contour can provide the pathes of the contour lines:
+  contour, z, x, y, $
+    levels = levels, $
+    path_info = path_info, $ ; info about the provided pathes (see below). If you provide here a variable contour will not draw.
+    path_xy = path_xy, $ ; variable for coordinates: fltarr(2,N_tot)
+    /path_data_coords, $ ; want to have data coordinates in data_xy instead of normalized coo's.
+    /path_double, $ ; you need double if eg x is time as julian day
+    /closed, $ ; close pathes along outline of the plotting area when isolines leave it.
+    /overplot ; avoid contour to rescale the axes - if you already had a plot or contour plot you want to reuse
+path_info is an array of CONTOUR_PATH_STRUCTURE. The number of elelemtns gives the number of sub pathes.
+Elements %%offset%% and %%N%% give the starting index and length of every isoline in path_xy.
+You can then use the pathes in poly_fill to do transparent hatch patterns:
+  for i = 0, n_elements(path_info)-1 do begin
+    ii = path_info[i].offset + lindgen(path_info[i].N)
+    polyfill, path_xy[0,ii], path_xy[1,ii], /line_fill, spacing=0.7, orientation=i*5, noclip=0
+  endfor ; i
+You could also use polyfill to put a byte pattern or wrap an image between the isolines ...
+  c = 255
+  pattern = [ $
+      [ 0, 0, 0, 0, 0, 0, 0 ], $
+      [ 0, 0, 0, c, 0, 0, 0 ], $
+      [ 0, 0, c, c, c, 0, 0 ], $
+      [ 0, c, c, c, c, c, 0 ], $
+      [ 0, 0, c, c, c, 0, 0 ], $
+      [ 0, 0, 0, c, 0, 0, 0 ], $
+      [ 0, 0, 0, 0, 0, 0, 0 ]  $
+    ]
+  for i = 0, n_elements(path_info)-1 do begin
+    ii = path_info[i].offset + lindgen(path_info[i].N)
+    polyfill, path_xy[0,ii], path_xy[1,ii], pattern=pattern, transparent=c-1, noclip=0, color='ff00ff'x
+  endfor ; i
+But i do not understand how the transparent thing works - in this example it does not work. And if i understood it right i need to provide IMAGE_COORD,
+see  NV5 help for [[https://www.nv5geospatialsoftware.com/docs/POLYFILL_Procedure.html#dg_routines_3604229493_877795|POLYFILL]].
 === color bar ===
-You can use contour also to make a **color bar**:
+You may want to have a color bar setting the colorshading in relation to values.
+You can use contour to make a **color bar**:
 A **horizontal** color bar at the bottom
@@ Line 3766: / Line 3851: @@
 If you want to interpolate only over certain dimensions they must be the last ones. You may use transpose to rearrange. Lets assume you have an array depending on x, y and time, i.e. z=fltarr(Nx,Ny,Nt) and you want to interpolate to certain x and y coordinates you can do this as follows:
-  z_ipol = transpose( interpolate( transpose(z_org,[2,0,1]) , ix_ipol , iy_ipol , /grid  ), [1,2,0] )
+  z_ipol = transpose( interpolate( transpose(z_org,[2,0,1]) , ix_ipol , iy_ipol , /grid, MISSING=!VALUES.f_nan  ), [1,2,0] )
+The /GRID flag allow to use different sizes for ix_ipol and iy_ipol and the MISSING keyword sets values of z_ipol outside the ranges of z_org to the missing value (no extrapolation).