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internal:administration:idl [2025/07/22 15:26] – [execute shell command : SPAWN] janinternal:administration:idl [2026/03/19 20:55] (current) – [contour] jan
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 IDL current reference @ NV5 Geospatial software :\\ IDL current reference @ NV5 Geospatial software :\\
-[[https://www.nv5geospatialsoftware.com/docs/routines-1.html| IDL  8.9. Reference @ NV5 ]]\\ +[[https://www.nv5geospatialsoftware.com/docs/routines-1.html| IDL  Reference @ NV5 ]]\\ 
-[[https://www.nv5geospatialsoftware.com/docs/funclisting.html| IDL  8.9. funclisting @ NV5]]\\ +[[https://www.nv5geospatialsoftware.com/docs/funclisting.html| IDL  funclisting @ NV5]]\\ 
-[[https://www.nv5geospatialsoftware.com/docs/WhatsNew.html| IDL  8.9. whats new @ NV5]]\\+[[https://www.nv5geospatialsoftware.com/docs/WhatsNew.html| IDL  whats new @ NV5]]\\
  
  
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   IF x eq 4 THEN BEGIN   IF x eq 4 THEN BEGIN
     print, 'x equals 4' $     print, 'x equals 4' $
-  END ELSE BEGIN+  ENDIF ELSE BEGIN
     print, 'x is not 4'     print, 'x is not 4'
-  END+  ENDELSE 
 + 
 +to keep track of your blocks you may extend the END statements with the statement the block started with, i.e. ENDIF for the block started afer an 'IF' or ENDELSE or ENDCASE, ENDWHILE, etc. 
 +The interpreter tells you then if a ENDxxx statement does not fit. 
 + 
 +You may nest i.e. build structures like IF ... THEN ... ELSE IF ... THEN ...\\ 
 + 
 + 
 +Alternatively you use the CASE statement: 
 + 
 +  CASE x of 
 +     1: <> 
 +    22: BEGIN 
 +        ... 
 +        END 
 +    ELSE: BEGIN 
 +          ... 
 +          END 
 +  ENDCASE 
 + 
 +if you want to handle several cases of x in one block you can do this:
  
-for safety you may extend the END statements with blocked statement i.e. ENDIF or ENDELSE+  CASE 1 of 
 +     x eq 1: begin 
 +       ... 
 +        END 
 +    (x eq 22) OR (x eq 23): begin 
 +        ... 
 +        END 
 +    ELSE: begin 
 +          ... 
 +          end 
 +  ENDCASE
  
-you may nest i.e. build structures like IF ... THEN ... ELSE IF ... THEN ... 
-or use the CASE statement. 
  
 Loops can be implented with FOR, WHILE or REPEAT as one-liners: Loops can be implented with FOR, WHILE or REPEAT as one-liners:
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   FOR i = 0,5 DO BEGIN   FOR i = 0,5 DO BEGIN
     PRINT, i     PRINT, i
-    END+    ENDFOR
      
   i = 0   i = 0
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     i = i+1     i = i+1
     PRINT, i     PRINT, i
-    END+    ENDWHILE
      
   i = 1   i = 1
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     i = i + 1      i = i + 1 
     PRINT, i     PRINT, i
-  END UNTIL i gt 5+  ENDREP UNTIL i gt 5
  
 to make coding a bit safer you may append the name of the loop command to the END statement, i.e. to make coding a bit safer you may append the name of the loop command to the END statement, i.e.
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   ENDREP    ENDREP 
  
-a PROCEDURE is a subroutine that may take parameters and change them. Its definition is started with the word PRO and ends with a END statement+a PROCEDURE is a subroutine that may take parameters and change them. Its definition is started with the word PRO and ends with an END statement
  
   PRO my_proc, text_str, x_value=x_value   PRO my_proc, text_str, x_value=x_value
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    1 => Plus sign (+)     1 => Plus sign (+) 
    2 => Asterisk (*)     2 => Asterisk (*) 
-   3 => Period (.) +   3 => one pixel dot (.) 
    4 => Diamond     4 => Diamond 
-   5 => Triangle 'up'+   5 => Triangle up (if symsize>0)  or down if symsize<0
    6 => Square     6 => Square 
    7 => X     7 => X 
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 ==== transparency ==== ==== transparency ====
  
-IDL does not know transparent overlays but on pixel based devices you can implement it with TVRD and TVRD.+IDL does not know transparent overlays but on pixel based devices you can implement it with TVRD and TV.
 Lets assume you want to put a bitmap BMP with size Nx, Ny at a position x0 y0 (pixels) with a tranparency factor of q_tra: Lets assume you want to put a bitmap BMP with size Nx, Ny at a position x0 y0 (pixels) with a tranparency factor of q_tra:
  
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 %%-dGraphicsAlphaBits=1%% avoids gridlines after rastering (http://www.idlcoyote.com/ps_tips/psstripes.html), \\ %%-dGraphicsAlphaBits=1%% avoids gridlines after rastering (http://www.idlcoyote.com/ps_tips/psstripes.html), \\
 %%-dEPSCrop%% crops the image at the bounding box. %%-dEPSCrop%% crops the image at the bounding box.
 +
 +You can execute gs from within IDL with the SPAWN command. As of IDL 9.x you need to prepend a ''unset LD_LIBRARY_PATH'' because IDL try to ensure its own (outdated) libraries for any spawn call:
 +  SPAWN, 'unset LD_LIBRARY_PATH; gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -r120 -dTextAlphaBits=4 -dGraphicsAlphaBits=1 -dEPSCrop -sOutputFile='+plt_name+'.png '+pl_name+'.eps', result, err_result
 +
 ==== postscript -> PDF ==== ==== postscript -> PDF ====
  
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   extrm_lev_max = +(machar()).xmax   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]].
  
  
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     /overplot     /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%%  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]]. 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
 +    /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
 +    path_info_i = path_info[i]
 +    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 ...
  
  
 === color bar === === 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 A **horizontal** color bar at the bottom
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 A one dimensional histogram is e.g. generated with A one dimensional histogram is e.g. generated with
  
-  histo = histogram( data , binsize=bin, locations = classes , /nan )+  binsize = 0.1 
 +  histo = histogram( data , binsize=binsize, locations = classes , /nan )
  
 the classes variable will contain the **lower borders** of the bins with the first bin starting at min(data). \\ the classes variable will contain the **lower borders** of the bins with the first bin starting at min(data). \\
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 or you write an own plot-histo procedure ... or you ask jan :-) ... or you write an own plot-histo procedure ... or you ask jan :-) ...
 +
 +
 +A histogram with geometric spacing, i.e. each bin is by a factor q_bin larger than the previous.\\
 +In this case data points lower or equal to zero are not allowed:
 +  q_bin = 2.0
 +  log_binsize = alog10(q_bin)
 +  histo = histogram( alog10(data[where(data gt 0)]), binsize=log_binsize, locations = log_bins, /nan )
 +  classes = 10^log_bins
 +
 +Plotting shall use then logarithmic scaling for the x-axes:
 +
 +    plot, classes , histo , psym=10, $
 +      xtitle = 'class (unit)', $
 +      ytitle = 'freq.', $
 +      /xlog
 +
  
 === 2-D histogram === === 2-D histogram ===
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   max_data_1 = max(data_1, /nan )   max_data_1 = max(data_1, /nan )
   N_bins_1 = fix((max_data_1-min_data_1)/bin_size_1)+1   N_bins_1 = fix((max_data_1-min_data_1)/bin_size_1)+1
-  bins_1 = min_data_1 + (findgen(N_bins_1) + 0.5) * bin_size_1 ; output of histo refers to lower border of bins => add 1/2binsize to center them in bin+  ; output of histo refers to lower border of bins => add 1/2binsize to center them in bin 
 +  bins_1 = min_data_1 + (findgen(N_bins_1) + 0.5) * bin_size_1 
        
   ; set bin-size, min and max and vector with bin-borders for data set 2   ; set bin-size, min and max and vector with bin-borders for data set 2
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   max_data_2 = max(data_2, /nan )   max_data_2 = max(data_2, /nan )
   N_bins_2 = fix((max_data_2-min_data_2)/bin_size_2)+1   N_bins_2 = fix((max_data_2-min_data_2)/bin_size_2)+1
 +  ; output of histo refers to lower border of bins => add 1/2binsize to center them in bin
   bins_2 = min_data_2 + (findgen(N_bins_2) + 0.5)*bin_size_2   bins_2 = min_data_2 + (findgen(N_bins_2) + 0.5)*bin_size_2
        
internal/administration/idl.1753198010.txt.gz · Last modified: by jan