Replot in ruby gnuplot

ruby-talk
1

I need to plot data in real time, reading a file over and over and
update a the screen. How to implement reread and replot?

require 'gnuplot'
class Plot
# Plot a surface of the data in file in realtime
  def realTimeSurfacePlot (plotFile, title, xLabel, yLabel, zLabel)
    Gnuplot::open do |gp|
      Gnuplot::SPlot.new(gp) do |plot|
  plot.title title
  plot.set "xlabel %s" %xLabel
  plot.set "ylabel %s" %yLabel
  plot.set "zlabel %s" %zLabel
  plot.set "grid"
  plot.set "pm3d"
  plot.data = [
    Gnuplot::DataSet.new("\""+plotFile+"\"") { |ds|

    }
  ]
      end
    end
end

Thank you

Lars

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2

Hi Lars,

I need to plot data in real time, reading a file over and over and
update a the screen. How to implement reread and replot?

Are you on Windows? Or, which OS?

I do something similar as you want to do (on Windows): I write data
coming from an ADC to Disk (using a c-programm), update line by line
each 1..60 seconds, and I read this file with Ruby and send the data
from Ruby to gnuplot, doing 2d-plots, updating the plot each time Ruby
reads a new data line.

For reading the file I use: file-tail.

For "real-time" plotting with gnuplot I took a lot from here and
transfered it to Ruby:
* http://users.softlab.ece.ntua.gr/~ttsiod/gnuplotStreaming.html

···

*
http://www.lysium.de/blog/index.php?/archives/234-Plotting-data-with-gnuplot-in-real-time.html
* https://news.ycombinator.com/item?id=3210793

I open a pipe to pgnuplot.exe:

@gp = "path_to_pgnuplot.exe"
...
@pipe = IO.popen(@gp, "w")
sleep 2
@pipe.puts "set xtics\n"
@pipe.puts "set ytics\n"
@pipe.puts "set style data #{ @linestyle }\n"
@pipe.puts "set grid\n"
...
@pipe.puts "plot \"-\" title 'CH1', \"-\" title 'CH2', \"-\" title
'CH3', \"-\" title 'CH4', \"-\" title 'CH5'"
...
@pipe.close

On Windows, I have a timeout problem with gnuplot;

# "Anti-timeout" workaround; put this at the very beginning of your
programm
puts "Starting dummy-instance of wgnuplot"
tmppipe = IO.popen(@gp, "w")
sleep 10
tmppipe.close

Hope it helps,
Axel

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3

Thanks, I'll give it a try tomorrow when I'm on a Windows box

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4

The suggestion works perfect for me. I used a separate thread and a
queue to communicate when new data i available instead of sleep.
It seems more flexible to use pipes than the wrapper, but the wrapper
maybe gives nicer code.

Thanks

Lars

···

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