How to reduce x ticks in matplotlib?-CodePudding

I have been working on pandas data that has too many time x points/ticks. I have found several solutions to reduce it, but my problem is I'm using two different data set with different time points. So, how to not only reduce the x-ticks as well as aligning these two data time points? Yes, I know sharex.

My plot generating code is following:

fig, (ax1, ax2,ax3,ax4) = plt.subplots(4, 1,figsize=(10,7), sharex="all")
fig.subplots_adjust(bottom=0.2)

ax1.plot( df.time, df['B'], color='k')
ax1.plot( df.time, df['Bx'], color='r')
ax1.plot( df.time, df['By'], color='b')
ax1.plot( df.time, df['Bz'], color='g')
ax1.xaxis.grid(True,alpha=0.3)
ax1.set_ylabel('Bx,By,Bz,B[nT]')

ax2.plot(df1.time, df1['v_total'],color='k')
ax2.plot(df1.time, df1['Vx'],color='r')
ax2.plot(df1.time, df1['Vy'],color='b')
ax2.plot(df1.time, df1['Vz'],color='g')
ax2.xaxis.grid(True,alpha=0.3)
ax2.set_ylabel('Vx,Vy,Vz,V[km/s]')

ax3.plot(df1.time, df1['n'],color='k')
ax3.xaxis.grid(True,alpha=0.3)
ax3.set_ylabel('Np[1/cm^3]')

ax4.plot(df1.time, df1['T'],color='k')
ax4.xaxis.grid(True,alpha=0.3)
ax4.set_ylabel('T[k]')
#loc = mdates.MinuteLocator([0,30])
#ax2.xaxis.set_major_locator(loc)
#ax2.xaxis.set_major_formatter(mdates.AutoDateFormatter(loc))
#ax3.xaxis.set_major_locator(loc)
#ax3.xaxis.set_major_formatter(mdates.AutoDateFormatter(loc))
#ax4.xaxis.set_major_locator(loc)
#ax4.xaxis.set_major_formatter(mdates.AutoDateFormatter(loc))
#ax2 = plt.gca()
#ax2.xaxis.set_major_locator(mdates.MinuteLocator(interval=10))
#ax2.xaxis.set_major_formatter(mdates.DateFormatter('%H:%M:%S')) 
#ax3 = plt.gca()
#ax3.xaxis.set_major_locator(mdates.MinuteLocator(interval=10))
#ax3.xaxis.set_major_formatter(mdates.DateFormatter('%H:%M:%S')) 
#ax4 = plt.gca()
#ax4.xaxis.set_major_locator(mdates.MinuteLocator(interval=10))
#ax4.xaxis.set_major_formatter(mdates.DateFormatter('%H:%M:%S')) 

fig.suptitle('Shock format')
plt.savefig('plot.png')
plt.savefig('plot1.pdf')
plt.show()

Here df is the one with many points and I want to reduce df x ticks/time points as well as aligning df1 to df. Hashtagged lines are my try, but it takes too long and giving me this warning "Locator attempting to generate 359569 ticks ([-113.5, ..., 2383.5]), which exceeds Locator.MAXTICKS (1000)."

The graph output is following

What my goal should look like is this

CodePudding user response：

I have created the data as I see fit as it seems difficult to provide data. The main point is that the byminute is the number of minutes, and the default value is 1 minute in the range (60). The interval specifies at what interval that minute increment should be displayed. So for the 15 minute increments, I used np.range(0,60,15) and two intervals. The result is 00 and 30 minute increments.

import pandas as pd
import numpy as np

date_rng = pd.date_range('2022-05-31 00:00:00', freq='1s', periods=43200)
df = pd.DataFrame({'datetime': pd.to_datetime(date_rng), 'value':np.random.randn(43200).cumsum()})

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

fig, (ax1,ax2,ax3,ax4) = plt.subplots(4, 1,figsize=(12,6), sharex="all")
fig.subplots_adjust(bottom=0.2)

ax1.plot(df.datetime, df['value'], color='b')
ax2.plot(df.datetime, df['value'], color='g')
ax3.plot(df.datetime, df['value'], color='r')
ax4.plot(df.datetime, df['value'], color='k')

minutes = mdates.MinuteLocator(byminute=np.arange(0,60,15),interval=2)
minutes_fmt = mdates.DateFormatter('%d %H:%M')
ax4.xaxis.set_major_locator(minutes)
ax4.xaxis.set_major_formatter(minutes_fmt)

ax4.tick_params(axis='x', labelrotation=45)
plt.show()