使用 matplotlib 的空白图

Question

I am doing a course in Python (I do not want them to solve the course questions or anything like that) and in this part, the course gives you a code so that you can visualize through graphics the number of robots (x-axis) and time- steps (y-axis), but when I run the code, it just doesn't graph anything. What should I do?

Sorry if it's a silly question but I'm not quite good with python visualization.

Here is some of the code:

def showPlot1(title, x_label, y_label):
    """
    What information does the plot produced by this function tell you?
    """
    num_robot_range = range(1, 11)
    times1 = []
    times2 = []
    for num_robots in num_robot_range:
        print("Plotting", num_robots, "robots...")
        times1.append(runSimulation(num_robots, 1.0, 20, 20, 0.8, 20, StandardRobot))
        times2.append(runSimulation(num_robots, 1.0, 20, 20, 0.8, 20, RandomWalkRobot))
    pylab.plot(num_robot_range, times1)
    pylab.plot(num_robot_range, times2)
    pylab.title(title)
    pylab.legend(('StandardRobot', 'RandomWalkRobot'))
    pylab.xlabel(x_label)
    pylab.ylabel(y_label)
    pylab.show()

showPlot1("Title", "Number of robots", "Time-steps")

Here is what it shows:

Here is what it prints:

Plotting 1 robots...
801.95
2019.15
Plotting 2 robots...
387.35
997.35
Plotting 3 robots...
256.4
732.7
Plotting 4 robots...
201.3
430.2
Plotting 5 robots...
158.25
366.3
Plotting 6 robots...
133.15
328.0
Plotting 7 robots...
113.65
276.1
Plotting 8 robots...
100.0
239.9
Plotting 9 robots...
85.9
191.85
Plotting 10 robots...
78.1
162.3

Thanks for your help!

Answer 1

I wrote a dummy runSimulation

def runSimulation(nrobots, a,b,c,d,e, randomrobot):
    if randomrobot:
        result = (450+100*rand())/(nrobots*(1+0.05-rand()*0.10))
    else:
        result = (900+200*rand())/(nrobots*(1+0.05-rand()*0.10))
    print("%10.3f"%result, end='')
    return result

and, using exactly the showPlot1 that you posted, I got a perfect plot

then I removed the return result statement from my dummy code and this is what I got (note the axes'limits, the same as in your figure)

My conclusion, you have not a consequential return something in your version of runSimulation — please check your code and please let us know if my guess is correct.

Answer 2

Your axes limits are not correct: you need x limits to be at least [1, 11] and y limits to be [0, 2200] (depending on the range of your simulation results, it could be even more) to be able to visualize your data.

Normally matplotlib automatically set these limits. Not sure why it did not do it in this case (prob the answer is in the code that you have not posted).

Try adding

  pylab.gca().set_xlim([0, 12])
  pylab.gca().set_ylim([0, 2200])

(see matplotlib reference here ) just before pylab.show() , maybe it will help.

Also, as in the comments, it would be better for everyone if you could post a minimal reproducible example - please do, if this answer does not help!