maint: Clean up m-files to follow Octave coding conventions. Try to trim long lines to < 80 chars. Use '##' for single line comments. Use '(...)' around tests for if/elseif/switch/while. Abut cell indexing operator '{' next to variable. Abut array indexing operator '(' next to variable. Use space between negation operator '!' and following expression. Use two newlines between endfunction and start of %!test or %!demo code. Remove unnecessary parens grouping between short-circuit operators. Remove stray extra spaces (typos) between variables and assignment operators. Remove stray extra spaces from ends of lines.

--- a/scripts/plot/draw/isocolors.m
+++ b/scripts/plot/draw/isocolors.m
@@ -54,7 +54,7 @@
 ##             "PlotBoxAspectRatio", [1 1 1]);
 ##   set (p, "FaceColor", "interp");
 ##   ## set (p, "FaceLighting", "flat");
-##   ## light ("Position", [1 1 5]); ## Available with JHandles
+##   ## light ("Position", [1 1 5]);  # Available with JHandles
 ## endfunction
 ##
 ## N = 15;    # Increase number of vertices in each direction
@@ -152,7 +152,7 @@
   endif
   switch (nargout)
     case 0
-      if (!isempty (pa))
+      if (! isempty (pa))
         set (pa, "FaceVertexCData", new_col);
       endif
     case 1