How do I change the range of the x-axis with datetimes in matplotlib?

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孤城傲影
孤城傲影 2020-11-28 08:44

I\'m trying to plot a graph of dates on the x-axis and values on the y-axis. It works fine, except that I can\'t get the range of the x-axis to be appropriate. The x-axis ra

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  • 2020-11-28 08:59

    Edit:

    Having seen actual data from the OP, all of the values are at the same date/time. So matplotlib is automatically zooming the x-axis out. You can still manually set the x-axis limits with datetime objects


    If I do something like this on matplotlib v1.3.1:

    import datetime
    import matplotlib.pyplot as plt
    
    x = [datetime.date(2014, 1, 29)] * 3 
    y = [2, 4, 1]
    
    fig, ax = plt.subplots()
    ax.plot_date(x, y, markerfacecolor='CornflowerBlue', markeredgecolor='white')
    fig.autofmt_xdate()
    ax.set_xlim([datetime.date(2014, 1, 26), datetime.date(2014, 2, 1)])
    ax.set_ylim([0, 5])
    

    I get:

    enter image description here

    And the axes limits match the dates that I specified.

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  • 2020-11-28 09:03

    With help from Paul H's solution, I was able to change the range of my time-based x-axis.

    Here is a more general solution for other beginners.

    import matplotlib.pyplot as plt
    import datetime as dt
    
    # Set X range. Using left and right variables makes it easy to change the range.
    #
    left = dt.date(2020, 3, 15)
    right = dt.date(2020, 7, 15)
    
    # Create scatter plot of Positive Cases
    #
    plt.scatter(
      x, y, c="blue", edgecolor="black", 
      linewidths=1, marker = "o", alpha = 0.8, label="Total Positive Tested"
    )
    
    # Format the date into months & days
    plt.gca().xaxis.set_major_formatter(mdates.DateFormatter('%m-%d')) 
    
    # Change the tick interval
    plt.gca().xaxis.set_major_locator(mdates.DayLocator(interval=30)) 
    
    # Puts x-axis labels on an angle
    plt.gca().xaxis.set_tick_params(rotation = 30)  
    
    # Changes x-axis range
    plt.gca().set_xbound(left, right)
    
    plt.show()
    

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