Convert x-axis from days to month in matplotlib

问题

i have x-axis which is in terms of days (366 days Feb was taken as 29 days) but instead I want to convert it in terms of months (Jan - Dec). What should i do...

def plotGraph():
    line, point = getXY()

    plt.plot(line['xlMax'], c='orangered', alpha=0.5, label = 'Minimum Temperature (2005-14)')
    plt.plot(line['xlMin'], c='dodgerblue', alpha=0.5, label = 'Minimum Temperature (2005-14)')

    plt.scatter(point['xsMax'].index, point['xsMax'], s = 10, c = 'maroon', label = 'Record Break Minimum (2015)')
    plt.scatter(point['xsMin'].index, point['xsMin'], s = 10, c = 'midnightblue', label = 'Record Break Maximum (2015)')

    ax1 = plt.gca() # Primary axes

    ax1.fill_between(line['xlMax'].index , line['xlMax'], line['xlMin'], facecolor='lightgray', alpha=0.25)

    ax1.grid(True, alpha = 1)

    for spine in ax1.spines:
        ax1.spines[spine].set_visible(False)

    ax1.spines['bottom'].set_visible(True)
    ax1.spines['bottom'].set_alpha(0.3)

    # Removing Ticks
    ax1.tick_params(axis=u'both', which=u'both',length=0)

    plt.show()

This is how the graph looks

回答1:

I think the quickest change might be to just set new ticks and tick labels at the starts of months; I found the conversion from day-of-the-year to month here, the first table:

import numpy as np
import matplotlib.pyplot as plt

fig, ax = plt.subplots()

x = range(1,367)
y = np.random.rand(len(range(1,367)))

ax.plot(x,y)

month_starts = [1,32,61,92,122,153,183,214,245,275,306,336]
month_names = ['Jan','Feb','Mar','Apr','May','Jun',
               'Jul','Aug','Sep','Oct','Nov','Dec'] 

ax.set_xticks(month_starts)
ax.set_xticklabels(month_names)

Note I assumed your days were numbered 1 to 366; if they are 0 to 365 you may have to change the range.

But I think usually a better approach is to get your days into some sort of datetime; this is more flexible and usually pretty smart. If say, your days were not confined to one year, it would be more complicated to associate day numbers with months.

This example uses datetime instead of integers. The dates are plotted on the x-axis directly, and then the DateFormatter and MonthLocator from matplotlib.dates are used to format the axis appropriately:

import datetime as dt
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import numpy as np

start = dt.datetime(2016,1,1)    #there has to be a year given, even if it isn't plotted
new_dates = [start + dt.timedelta(days=i) for i in range(366)]

fig, ax = plt.subplots()

x = new_dates
y = np.random.rand(len(range(1,367)))

xfmt = mdates.DateFormatter('%b')
months = mdates.MonthLocator()
ax.xaxis.set_major_locator(months)
ax.xaxis.set_major_formatter(xfmt)

ax.plot(x,y)

来源：https://stackoverflow.com/questions/62360855/convert-x-axis-from-days-to-month-in-matplotlib

标签

python

matplotlib