How to autoscale the yrange of gnuplot in python - gnuplot

Question

I have a python script that I write out a .gnu file and it plots a .png file. I am trying to make the yrange more dynamic by setting the range to be 5% of the max and min.
What am I doing wrong?
This code will not run like this.
#-- write out .gnu file
self.output = textwrap.dedent('''\
set terminal png size 800,600
set output "{0}"
set grid
set xlabel "Cycle"
set title "{1}"
set xtics ({2})
set yrange[GPVAL_Y_MIN:GPVAL_Y_MAX]
plot ''').format(self.figurename, self.title, ",".join(plot_data.keys()), self.styletype, self.datafile)
for n in range(0,max_num_lines):
tmp_str = " ".join(['"{2}"','using','1:'+str(n+2),'title',"'"+self.titles[n+1]+"'",'w linespoints {1}']).format(self.figurename, self.linecombos[n], self.datafile)
if n!=max(range(0,max_num_lines)):
tmp_str += ", "
self.output += tmp_str
pass

Answer 1

The internal variables GPVAL_Y_MIN/GPVAL_Y_MAX are not initialized until you actually plot something. To circumvent this, you might use the stats command which analyzes a file and provides the desired min/max values via the STATS_min_y/STATS_max_y variables:
self.output = textwrap.dedent('''\
set terminal png size 800,600
set output "{0}"
set grid
set xlabel "Cycle"
set title "{1}"
set xtics ({2})
#analyze the file and adjust y-range
stats "{3}" nooutput
set yrange[STATS_min_y:STATS_max_y]
plot ''').format(self.figurename, self.title, ",".join(plot_data.keys()), self.styletype, self.datafile)