How to change polar lines by different colors with respect to the interval with gnuplot

Question

I'd like to change this polar plot by using Gnuplot as following:

1. changing line color (radial lines and their semi circle edges) by different colors with respect to the range. For example, A to F interval as red, G to L as blue, and M to S keeping black

Below, I'm providing my code and I'd appreciate if someone give a hand with that.

`set decimalsign '.'

unset border
set polar
set angles degrees #set gnuplot on degrees instead of radians

set style line 10 lt rgb "black" lw 4.0 #redefine a new line style for the grid

set grid polar 20 #set the grid to be displayed every 20 degrees
set grid ls 10

set rrange [0:0.3]
set rtics 0, 0.05, 0.2 format "%.2f"

set size square 

set_label(x, text) = sprintf("set label '%s' at (0.22*cos(%f)), (0.22*sin(%f)) center", text, x, x) #this places a label on the outside

#here all labels are created
eval set_label(0, "A")
eval set_label(20, "B")
eval set_label(40, "C")
eval set_label(60, "D")
eval set_label(80, "E")
eval set_label(100, "F")
eval set_label(120, "G")
eval set_label(140, "H")
eval set_label(160, "I")
eval set_label(180, "J")
eval set_label(200, "K")
eval set_label(220, "L")
eval set_label(240, "M")
eval set_label(260, "N")
eval set_label(280, "O")
eval set_label(300, "P")
eval set_label(320, "Q")
eval set_label(340, "S")


set style line 11 lt rgb "blue" lw 10 pt 6 ps 6

plot "-" u 1:2 w lp ls 11
0    0.1499
020   0.1517
040   0.1474
060   0.1520
080   0.1526
100  0.1501
120  0.1491
140  0.1530
160  0.1515
180  0.1519
200  0.1534
220  0.1509
240  0.1501
260  0.1520
280  0.1481
300  0.1523
320  0.1529
340  0.1505
360    0.1499`

Answer 1

Here would be my suggestion. You can shorten the placing of the labels a bit. I am not aware that you can set individual colors for grid lines, so you have to color them "manually". Check the example below as a starting point. I assumed that after Q there is coming R not S .

Code: (edit: colored border added)

### polar graph with colored grid lines
reset session

$Data <<EOD
0    0.1499
020   0.1517
040   0.1474
060   0.1520
080   0.1526
100  0.1501
120  0.1491
140  0.1530
160  0.1515
180  0.1519
200  0.1534
220  0.1509
240  0.1501
260  0.1520
280  0.1481
300  0.1523
320  0.1529
340  0.1505
360    0.1499
EOD

set size square 
unset border
set polar
set angles degrees
unset label
unset tics
unset key 

set style line 10 lt rgb "black" lw 1
set style line 11 lt rgb "blue" lw 4 pt 6 ps 1

set rrange [0:0.2]
set rtics 0, 0.05, 0.2 format "%.2f"

Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
N=18
set grid polar 360./N ls 10
set for [a=1:N] ttics (Alphabet[a:a] (a-1)*360./N)    # set ttic labels

R=0.2
myColors   = '0xff0000 0x00ffff 0x000000'
myColor(n) = word(myColors,(n-1)/(N/3)+1)   #  !!! integer division

set for [a= 1: N] object a circle at 0,0 size R arc [(a-1)*360./N:a*360./N] fc rgb myColor(a) lw 2 front wedge

plot $Data u 1:2 w lp ls 11
### end of code

Result: