pythonmatplotlibaxisxticksyticks

Changing the tick frequency on the x or y axis


I am trying to fix how python plots my data. Say:

x = [0, 5, 9, 10, 15]
y = [0, 1, 2, 3, 4]

matplotlib.pyplot.plot(x, y)
matplotlib.pyplot.show()

The x axis' ticks are plotted in intervals of 5. Is there a way to make it show intervals of 1?


Solution

  • You could explicitly set where you want to tick marks with plt.xticks:

    plt.xticks(np.arange(min(x), max(x)+1, 1.0))
    

    For example,

    import numpy as np
    import matplotlib.pyplot as plt
    
    x = [0,5,9,10,15]
    y = [0,1,2,3,4]
    plt.plot(x,y)
    plt.xticks(np.arange(min(x), max(x)+1, 1.0))
    plt.show()
    

    (np.arange was used rather than Python's range function just in case min(x) and max(x) are floats instead of ints.)


    The plt.plot (or ax.plot) function will automatically set default x and y limits. If you wish to keep those limits, and just change the stepsize of the tick marks, then you could use ax.get_xlim() to discover what limits Matplotlib has already set.

    start, end = ax.get_xlim()
    ax.xaxis.set_ticks(np.arange(start, end, stepsize))
    

    The default tick formatter should do a decent job rounding the tick values to a sensible number of significant digits. However, if you wish to have more control over the format, you can define your own formatter. For example,

    ax.xaxis.set_major_formatter(ticker.FormatStrFormatter('%0.1f'))
    

    Here's a runnable example:

    import numpy as np
    import matplotlib.pyplot as plt
    import matplotlib.ticker as ticker
    
    x = [0,5,9,10,15]
    y = [0,1,2,3,4]
    fig, ax = plt.subplots()
    ax.plot(x,y)
    start, end = ax.get_xlim()
    ax.xaxis.set_ticks(np.arange(start, end, 0.712123))
    ax.xaxis.set_major_formatter(ticker.FormatStrFormatter('%0.1f'))
    plt.show()