GNUplot stdin, how to plot multiple lines?

Question

OK so I am piping data into GNUplot in the form of, e.g:

2013-11-04 20:00:12,875,350,112,29,38,4,44,10,632,121

~~I have set the following in my Python code:~~

gnuplot.stdin.write("plot '-' u 1:2 t 'aa',\ '' u 1:3 t 'aa in',\ '' u 1:4 t 'bb',\ '' u 1:5 t 'bb in',\ '' u 1:6 t 'cc',\ '' u 1:7 t 'cc in',\ '' u 1:8 t 'dd',\ '' u 1:9 t 'dd in',\ '' u 1:10 t 'ee';\n")

However I keep getting errors such as:

gnuplot> plot '-' u 1:2 t 'aa',    '' u 1:3 t 'aa in',    '' u 1:4 t 'bb',    '' u 1:5 t 'bb in',    '' u 1:6 t 'cc',    '' u 1:7 t 'cc in',    '' u 1:8 t 'dd',    '' u 1:9 t 'dd in',    '' u 1:10 t 'ee';
                                                   ^
         line 1271: warning: Skipping data file with no valid points

~~Any ideas?~~

~~###UPDATE:###~~

Based on @Christoph's feedback; here's the code I'm currently using:

cur.execute(sql) data = cur.fetchall() c = 0 for k in data: dataElement = data[c] gnuplot.stdin.write("plot '-' u 1:2 t 'aa',\ '' u 1:3 t 'aa in',\ '' u 1:4 t 'bb',\ '' u 1:5 t 'bb in',\ '' u 1:6 t 'cc',\ '' u 1:7 t 'cc in',\ '' u 1:8 t 'dd',\ '' u 1:9 t 'dd in',\ '' u 1:10 t 'ee';\n") gnuplot.stdin.write("%s,%i,%i,%i,%i,%i,%i,%i,%i,%i,%i\n" % dataElement[:]) gnuplot.stdin.write("e\n") c = c + 1

@Bernhard No. I get the same errors as above, i.e.: gnuplot> plot '-' u 1:2, '' u 1:3, '' u 1:4, '' u 1:5, '' u 1:6, '' u 1:7, '' u 1:8, '' u 1:9, '' u 1:10; — tlre0952b
– tlre0952b, Commented Nov 22, 2013 at 15:02
@Christoph I have asked a more specific question with more focus as suggested (by you). — tlre0952b
– tlre0952b, Commented Nov 22, 2013 at 15:34

Christoph · Accepted Answer · 2013-11-22 16:44:41Z

3

You must write an own data block for each '-'. The '' saves you only from retyping the file name, but doesn't reuse the data. Consider e.g. the following gnuplot script:

plot '-', '-'
2
4
6
e
10
12
14
e

Also make sure, that your delimiter is set properly: set datafile separator ','.

Here is a minimal python script, which plots two data sets from stdin, with the columns separated by comma:

#!/usr/bin/env python
import subprocess

gnuplot = subprocess.Popen(["gnuplot"], stdin=subprocess.PIPE)

gp_wrt = gnuplot.stdin.write

gp_wrt("set terminal pngcairo\n")
gp_wrt("set output 'test.png'\n")
gp_wrt("set datafile separator ','\n")
gp_wrt("plot '-' with lines title 'mytitle',\
'-' with lines title 'other title'\n")
for i in range(11):
    gp_wrt("{},{}\n".format(i, i**2))
gp_wrt("e\n")

for i in range(11):
    gp_wrt("{},{}\n".format(i, (0.5*i)**2))
gp_wrt("e\n")

So for your data it may look like

gnuplot.stdin.write("plot '-' u 1:2 t 'aa',\
    '' u 1:3 t 'aa in',\
    '' u 1:4 t 'bb',\
    '' u 1:5 t 'bb in',\
    '' u 1:6 t 'cc',\
    '' u 1:7 t 'cc in',\
    '' u 1:8 t 'dd',\
    '' u 1:9 t 'dd in',\
    '' u 1:10 t 'ee';\n")

for i in range(10):
    for dataElement in data:
        gnuplot.stdin.write("%s,%i,%i,%i,%i,%i,%i,%i,%i,%i,%i\n" % dataElement[:])
    gnuplot.stdin.write("e\n")

But in that case you could simply use:

gnuplot.stdin.write("plot '-' u 1:2 t 'aa',\
    '' u 1:2 t 'aa in',\
    '' u 1:2 t 'bb',\
    '' u 1:2 t 'bb in',\
    '' u 1:2 t 'cc',\
    '' u 1:2 t 'cc in',\
    '' u 1:2 t 'dd',\
    '' u 1:2 t 'dd in',\
    '' u 1:2 t 'ee';\n")

for i in range(10):
    for dataElement in data:
        gnuplot.stdin.write("%s,%i\n" % (dataElement[0], dataElement[i])
    gnuplot.stdin.write("e\n")

i.e. each time you write only the relevant columns.

edited Nov 22, 2013 at 16:44

answered Nov 22, 2013 at 7:19

Christoph

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11 Comments

tlre0952b Over a year ago

I have put gnuplot.stdin.write("e\n") after each time the data is sent and I am getting somewhere with this. All the relevant data points are now showing up with respective legends. However, I am a little stuck; the first row have been accepted but none of the following rows of data are. I do not follow your plot '-', '-' part?

Christoph Over a year ago

That was meant as a pure gnuplot script and should show, that for two '-' parts you need to send the data twice, each time terminated with an e. I added a minimal python script, which plots two data sets coming from stdin.

tlre0952b Over a year ago

I have 440 lines to submit through stdin to gnuplot. Are you telling me I need 439 '-', after plot ending with '-'; and then looping through the data to be submitted?

Christoph Over a year ago

With 'lines' do you mean a line in the plot (severy connected points) or a row in the data set? And if you indeed have 440 lines to plot, then you need as many '-', but I can't believe that, especially with all of them having keys :) If you have 440 rows in a data set, which are connected together to a single line in the plot, then you need only a single '-'.

tlre0952b Over a year ago

I have included the code in my original question; that's what I think you mean. Is it?

|

tlre0952b · Accepted Answer · 2013-11-22 21:01:19Z

1

The following code solved it:

gnuplot.stdin.write("plot '-' u 1:2 t 'aa', " + \
            " '-' u 1:2 t 'aa in', " + \
            "'-' u 1:2 t 'bb', " + \
            "'-' u 1:2 t 'bb in', " + \
            "'-' u 1:2 t 'cc', " + \
            "'-' u 1:2 t 'cc in', " + \
            "'-' u 1:2 t 'dd', " + \
            "'-' u 1:2 t 'dd in', " + \
            "'-' u 1:2 t 'ee', " + \
            "'-' u 1:2 t 'ee in';\n")

for n in range(10):
    for dataElement in data:        
        a = n + 1
        if a == 11:
            break
        else:
            gnuplot.stdin.write("%s,%i\n" % (dataElement[0],dataElement[a]))
    gnuplot.stdin.write("e\n")
gnuplot.stdin.flush()

answered Nov 22, 2013 at 21:01

tlre0952b

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Dima · Accepted Answer · 2013-11-30 08:04:25Z

0

Pipe space-delimited data to this tool instead:

https://github.com/dkogan/feedgnuplot

It'll feed gnuplot thing the right commands, and make plots. Use --dump if you want to get a gnuplot script out of it.

answered Nov 30, 2013 at 8:04

Dima

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