How to plot events with minute precision on hourly plots

Question

I have an hourly plot generated with matplotlib. I need to plot an event which goes for example, from 09:00 to 10:45. When I try to do it, using axvspan I obtain a bar from 9:00 to 10:00. How could I obtain the longer one?

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec
import datetime as dt
import pandas as pd

now_date = dt.datetime(2018,10,1,9)
d_tw_ini = now_date - dt.timedelta(hours = 1)
d_tw_fin = now_date + dt.timedelta(hours = 3)
  
dts = pd.date_range(start=d_tw_ini, end=d_tw_fin, freq='1H', name='ini', closed='left')
data=pd.DataFrame({'val':[0.5,0.4,0.7,0.9]})

ev1=[dt.datetime(2018,10,1,9,5),dt.datetime(2018,10,1,10,50)]

data['t']=dts.values
data.set_index('t',inplace=True)

fig = plt.figure()
gs = GridSpec(1, 1)
ax_1 = fig.add_subplot(gs[0, 0])

data.plot(ax=ax_1, y='val')
ax_1.axvspan(ev1[0],ev1[1], alpha=0.3, color= 'red')

Result

Asked By: jgarci7777

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Source

Answer 1

Juan, it looks when you used pandas to plot, the hourly indexing seems to cause issues with how axvspan gets plotted.

I replaced

data.plot(ax=ax_1, y='val')

with

ax_1.plot(data.index, data['val'])

which generates the image below, but unfortunately you lose the automated x-axis formatting.

Adding the two lines below will result in the same date formatting as your example.

ax_1.set_xticks([x for x in data.index])
ax_1.set_xticklabels([str(x)[11:16] for x in data.index])

Below is the full code to produce the above plot.

import matplotlib.pyplot as plt
from matplotlib.gridspec import GridSpec
import datetime as dt
import pandas as pd

now_date = dt.datetime(2018,10,1,9)
d_tw_ini = now_date - dt.timedelta(hours = 1)
d_tw_fin = now_date + dt.timedelta(hours = 3)

dts = pd.date_range(start=d_tw_ini, end=d_tw_fin, freq='1h', name='ini', 
closed='left')
data=pd.DataFrame({'val':[0.5,0.4,0.7,0.9]})

ev1=[dt.datetime(2018,10,1,9,5,0),dt.datetime(2018,10,1,10,50,0)]

data['t']=dts.values
data.set_index('t',inplace=True)

fig = plt.figure()
gs = GridSpec(1, 1)
ax_1 = fig.add_subplot(gs[0, 0])

# modified section below
ax_1.plot(data.index, data['val'])
ax_1.axvspan(ev1[0],ev1[1], alpha=0.3, color= 'red')

ax_1.set_xticks([x for x in data.index])
ax_1.set_xticklabels([str(x)[11:16] for x in data.index])

plt.show()

Answered By: daronjp

How to plot events with minute precision on hourly plots

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