Recent changes to polar coordinates in gnuplot 5.1

[sfeam <sf...@us...>]

The development version of gnuplot (5.1) now contains a set of fixes, 
improvements, and additions to the support for polar coordinates.
Please give them a test and report any problems.


- The r axis now has a full set of range, label, and tic properties
	set rrange [min:max]
	set log r
	set rlabel "R-axis"
	set rtics
	set grid [no]rtics [no]mrtics


- New commands
	
  "set ttics" and "set mttics" control placement and labeling of tics
  around the perimeter of a polar plot

  "set border polar" draws a circular solid line at the perimeter


- Use of polar coordinates to position labels, arrows, objects

  You can now use the keyword "polar" when specifying coordinates for
  any position.  For example to place a labeled arrow on a polar plot:
	theta = 15; r = 1.23
	set arrow 1 from polar 0,0 to polar theta, r 
	set label 1 at polar theta,r "Current place" offset 1,1


- New demos
	http://gnuplot.sourceforge.net/demo_5.1/ttics.html
	http://gnuplot.sourceforge.net/demo_5.1/solar_path.html


- Internal code reorganization

  There is now a single utility routine polar_to_xy(theta, r, &x, &y)
  to convert from polar coordinates to cartesian coordinates.
  It is used for both data input and plot layout.  If you add new 
  code that supports polar coordinates please use this routine.