gnuplot-info

[Gnuplot-info] How to dynamically specify color for drawing circle in Gnuplot4.3

[lilu29 <lul...@gm...>]

Hi, everyone
Gnuplot4.3 has a new type for drawing circle, and in its manual, it says "An
optinal 4th column may be used to specify color information". But it doesn't
give any example of using this function. All its examples for drawing circle
are specifying color statically.

What I want to do is: I want to draw circles using following input data,
each circle is defined by one line, the 4th column is the painting color.
What should I do???? I tried 
plot "file" using 1:2:3:4 with circles lc rgb $4
plot "file" using 1:2:3:4 with circles lc rgb variable
they all don't work.
Can someone give me some hints?

Thank you very much!

My input data's format is:
x y radius color
2 3  4      "yellow"
1 1  5       "red"
.............



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Re: [Gnuplot-info] How to dynamically specify color for drawing circle in Gnuplot4.3

[lilu29 <lul...@gm...>]

Hi, guys
Nobody answers this question, so I spent nearly 4 hours to hack Gnuplot in
order to find out how to use this function for specifying color from data
file. I didn't read its source code before, so starting from the scratch.

The requirement:
Gnuplot4.3 source code,
grep 
That's enough.

This post only represents my own opinion, so there may be some faults,
welcome to point them out.
Because, when I hacked the source code, I added a  few print statements,
maybe there exists some wrong line numbers.
But I wrote out the full function names and variable names, wrong line
numbers don't effect reading.

1) Where is the main function for starting
The entry main function is in "plot.c": int gnu_main(), or int main()

2) Which function plots circles or other objects
void place_objects() : graphics.c
In this function, you can find "case OBJ_CIRCLE". You can also see
"do_arc(x1, y1, radius, e->arc_begin, e->arc_end,0)"

do_arc() really draws circles.:term.c
One of its parameters "style" controls the drawing style.

3) The drawing style mentioned in (2) is set in place_objects and actually
from object* listhead which is the first parameters in this function. We can
also find out that this parameter is a list of objects, so gnuplot plots
objects in this list one by one.

4) Which function invokes place_objects() and give parameter "object*
listhead"
void do_plot(): graphics.c
On line 1567 of graphics.c, it invokes place_object(first_object,****),
first_object is a global variable which a head of object list.
void refresh_request(): command.c --this function invokes
"do_plot(first_plot)"
first_plot is also a global variable set in eval_plots(): plot2d.c
On line 1414 in this file, we see top_ptr=&(first_plot)
In this file, we also see a imporant variable "struct curve_poins*
this_plot", this variable specifies the drawing style. We can find many
drawing properties set in this function. But the most important statement is
line 1993:(get_data(this_plot))

5)get_data(this_plot): plot2d.c
In this function, we can find "TBOOLEAN variable_color", it decides whether
we can specify color dynamically.
Another important variable for setting color value (RGB value) is "double
variable_color_value ". This value is real color value for drawing objects.

This function also points out:
the min_cols and max_cols  of data file for drawing circle are 3 and 4.
(line 472)
The comment says /*3+ possible variable color*/
So we really confirm that color for each circle can be set at the 4th column 
of  data file.

we can see that the value of variable_color_value is from data file:
"variable_color_value = v[--j]"
v[] is a array read from data file. This array is also processed through
some function specified at "using func($1):func($2)***"

6) Now the important is: how to let variable_color ==true
on line 340 in plot2d.c, we can find out two conditions can make this value
true.
We track the first condition,
"current_plot->lp_properties.pm3d_color.type==TC_RGB"

color.type is set at "parse_colorspec()", while "parse_colorspec()" is
invoked in lp_parse(). Both functions are in misc.c.
>From " lp_parse()", we know that we need to specify "lt" in the command line
to invoke parse_colorspec()
>From "parse_colorspec" we need to specify "rgb " in command.

In conclusion, to set circle color from data file, we should:
a, the format of data file
x y radius color_clue
 
ps: color_clue can be the real RGB value or any varialbe which we can
calculate RGB from it

b, the rgb command
plot "data_file" using 1:2:3:yourColorFunc($4, or the total four columns)
with circles lt rgb var
or
plot "data_file" using 1:2:3:yourColorFunc($4, or the total four columns)
with circles lt rgbcolor var
or
plot "data_file" using 1:2:3:yourColorFunc($4, or the total four columns)
with circles lt rgbcolor variable
or
plot "data_file" using 1:2:3:yourColorFunc($4, or the total four columns)
with circles lt rgb variable

(rgb==rgbcolor; var==variable)
This command is enough, we do not need to do any other command.



lilu29 wrote:
> 
> Hi, everyone
> Gnuplot4.3 has a new type for drawing circle, and in its manual, it says
> "An optinal 4th column may be used to specify color information". But it
> doesn't give any example of using this function. All its examples for
> drawing circle are specifying color statically.
> 
> What I want to do is: I want to draw circles using following input data,
> each circle is defined by one line, the 4th column is the painting color.
> What should I do???? I tried 
> plot "file" using 1:2:3:4 with circles lc rgb $4
> plot "file" using 1:2:3:4 with circles lc rgb variable
> they all don't work.
> Can someone give me some hints?
> 
> Thank you very much!
> 
> My input data's format is:
> x y radius color
> 2 3  4      "yellow"
> 1 1  5       "red"
> .............
> 
> 
> 
> 

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Re: [Gnuplot-info] How to dynamically specify color for drawing circle in Gnuplot4.3

[v_2e <v_...@uk...>]

  Hello!

TonyM wrote:
> 
> I'm having the same problem.
> Can you please provide a working example of both the data and the code
> used to run.
> 
  I can provide my working example. It is very simple.
I have a test_map.txt file with contents like this:
0 0 5 7
-90 0 2 4
90 0 2 4
-120 0 1 3
The columns mean x-coordinate, y-coordinate, radius and a color
respectively.
  And I can easily plot the circles from such file just by using this
command line:
$ gnuplot -persist -e 'plot "test_map.txt" using 1:2:3:4 with circles lc
variable'
  Or if I would like to have filled circles, I can use:
$ gnuplot -persist -e 'plot "test_map.txt" using 1:2:3:4 with circles fill
solid lc variable'
  And that is all! :)
  Hope, it will help you!

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Re: [Gnuplot-info] How to dynamically specify color for drawing circle in Gnuplot4.3

[exprexxo <exp...@gm...>]

Here is another example without a file

set title "A Venn Diagram"
unset border
unset xtics
unset ytics
set size ratio -1
set xrange [-10:10]
set yrange [-10:10]
plot '-' using 1:2:3:4 with circles lc rgb variable fs transparent solid
0.15 noborder
 2 2 4 1
 -2 2 5 200
 0 -2  5 3
 e

However I can not figure out what numbers I should be using for RGB other
than 200 gives me blue.
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Re: [Gnuplot-info] How to dynamically specify color for drawing circle in Gnuplot4.3

[Thomas S. <t.s...@fz...>]

rgbcolors are made of 3 components - red, green, and blue,
represented as hexadecimal values: #RRGGBB
the 3 color values are in the range 0-255, so the rgbcolor
as a decimal value is: 65536 * red + 256 * green + blue

you read in this decimal value in your plot command, a value
of '200' means that the red and green components are zero
- the number is too small - so the circle is blue.

some rgbcolor value examples:
red: 65536*255 = 16711680
green: 256*255 = 65280
blue: 255

instead of rgbcolors you could use a color palette:
plot ... linecolor palette ...


exprexxo wrote:
> 
> Here is another example without a file
> 
> set title "A Venn Diagram"
> unset border
> unset xtics
> unset ytics
> set size ratio -1
> set xrange [-10:10]
> set yrange [-10:10]
> plot '-' using 1:2:3:4 with circles lc rgb variable fs transparent solid
> 0.15 noborder
>  2 2 4 1
>  -2 2 5 200
>  0 -2  5 3
>  e
> 
> However I can not figure out what numbers I should be using for RGB other
> than 200 gives me blue.
> 

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Re: [Gnuplot-info] How to dynamically specify color for drawing circle in Gnuplot4.3

[exprexxo <exp...@gm...>]

Perfect that was exactly what I needed to make the example even better,
So here is a Circle Example that does a Venn diagram with a red, blue and a
green colored circle 

set title "A Venn Diagram"
unset border
unset xtics
unset ytics
set size ratio -1
set xrange [-10:10]
set yrange [-10:10]
plot '-' using 1:2:3:4 with circles lc rgb variable fs transparent solid
0.15 noborder
 2 2 4 167116800
 -2 2 5 65280
 0 -2  5 255
 e

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