Unexplained label on plot

Community matplotlib-users
#1

Hi All,

An extra label is appearing on the plot I'm generating. I wonder if anyone
could explain what it means/how to get rid of it?

The plot is available at http://test.outpost.org.uk/example.png - the
unexplained label is the '+4.05674e7' in the upper right hand corner. This
value doesn't appear to be related to what I'm doing numerically.

My plotting code is below (should probably tidy this up!):

# Plot Results
lines1 = []
plot1 = pylab.subplot(211)
lines1.extend(pylab.plot(In, thrust / g, 'b-'))
pylab.ylabel('Thrust (kgf)')
pylab.grid(True)
ax2 = pylab.twinx()
lines1.extend(pylab.plot(In, inputFlow * 60000, 'g--'))
pylab.ylabel('Flow (lpm)')
pylab.legend(lines1, ('Thrust', 'Flow'), 2) #(0.02,0.8)
plot1.set_xticklabels([])
pylab.title('%s / %s (%d lpm) / %d bar' % (self.thruster.name,
self.valve.name, self.valve.ratedFlow * 60000, sysPres * 10**-5))

lines2 = []
plot2 = pylab.subplot(212)
lines2.extend(pylab.plot(In, thrusterPower * 0.001, 'c--'))
lines2.extend(pylab.plot(In, valvePower * 0.001, 'r:'))
lines2.extend(pylab.plot(In, totalPower * 0.001, 'm-'))
pylab.ylabel('Power (kW)')
pylab.grid(True)
ax4 = pylab.twinx()
lines2.extend(pylab.plot(In, 1000 * efficiency / g, 'y-'))
pylab.ylabel('Efficiency (kgf/kW)')
pylab.xlabel('Control Current (normalised)')
pylab.legend(lines2, ('Thruster', 'Valve', 'Total', 'Efficiency'), 2)
#(0.02,0.6)

pylab.savefig(filename, orientation='landscape')
pylab.clf()

Thanks in advance for any help/advice.

-Stuart

···

-----------------------------
Stuart Yarrow

#2

Stuart Yarrow wrote:

Hi All,

An extra label is appearing on the plot I'm generating. I wonder if anyone
could explain what it means/how to get rid of it?

The plot is available at http://test.outpost.org.uk/example.png - the
unexplained label is the '+4.05674e7' in the upper right hand corner. This
value doesn't appear to be related to what I'm doing numerically.

# Plot Results
lines1 = []
plot1 = pylab.subplot(211)
lines1.extend(pylab.plot(In, thrust / g, 'b-'))
pylab.ylabel('Thrust (kgf)')
pylab.grid(True)
ax2 = pylab.twinx()
lines1.extend(pylab.plot(In, inputFlow * 60000, 'g--'))

Couldn't it be because of "inputFlow * 60000", which may cause the plotted values to be large (so it is related to what you do numerically)? The same happens for e.g. plot(array([1,2,3])+1e5), i.e. if the values' changes are small compared to their magnitude. Without that, the tick numbers would read 100001.0, 100002.0, 100003.0 in this example, which may not look very pretty.

HTH

···

--
cheers,
steve

Random number generation is the art of producing pure gibberish as quickly as possible.

#3

Steve,

Thank you, I think you are right in general (the multiply by 60000 is
correct though). Since mucking about with my code a bit more it has
disappeared. Just strange to see an additive, as opposed to
multiplicative, error given the type of calcs that I am doing, hence my
doubting the meaning of the label.

many thanks

-Stuart

Steve Schmerler said:

···

lines1.extend(pylab.plot(In, inputFlow * 60000, 'g--'))

Couldn't it be because of "inputFlow * 60000", which may cause the
plotted values to be large (so it is related to what you do
numerically)? The same happens for e.g. plot(array([1,2,3])+1e5), i.e.
if the values' changes are small compared to their magnitude. Without
that, the tick numbers would read 100001.0, 100002.0, 100003.0 in this
example, which may not look very pretty.

-----------------------------
Stuart Yarrow