Question

I’ve a python script who generate a graphic with gnuplot. But I’ve an error:

gnuplot> plot
^
line 0: function to plot expected

    g=Gnuplot.Gnuplot(persist=1)
    g.title('Read&Write Performance')
    g.xlabel('minutes')
    g.ylabel('MB/s')
    g('set term png')
    g('set out')
    g('set yrange [0:70]')
    d1=Gnuplot.Data(self.time,self.list1,title="perfr", with_="line")
    d2=Gnuplot.Data(self.time,self.list2,title="perfw", with_="line")
    time.sleep(2)
    g.hardcopy('bench.png',terminal = 'png')
    g.reset()

self.list1= [12, 15, 17]
self.list2 = [43, 48, 49]

I don’t understand why I’ve this error.

Thanks 🙂

Answer 1

After a very brief look at the source, it seems that g.plot() does not send the plot to a window (e.g. x11), but to wherever gnuplot is currently configured to send the plot. So, (I think) the easiest solution is —

g('set terminal png')
g('set output "bench.png"')
g.plot(d1)  #d1 should not be in "bench.png"
#This might work to plot both datasets together ... g.plot(d1,d2)  

This should work as long as the internals of gnuplot-py don’t reset the gnuplot script whenever a plot command is issued. I highly doubt this is the case since the __call__ method seems to be such an important part of the API.