I want to make a program that monitors my 5000 meters progress. Inspired by this and this, I tried to make it work by combining some of the answers without any luck.
from __future__ import division
from matplotlib import pyplot as plt
from matplotlib.ticker import FuncFormatter
import matplotlib.dates as mdates
import numpy as np
import datetime as dt
def equidate_ax(fig, ax, dates, fmt="%d.%m.%Y", label="Date"):
N = len(dates)
def format_date(index, pos):
index = np.clip(int(index + 0.5), 0, N - 1)
return dates[index].strftime(fmt)
ax.xaxis.set_major_formatter(FuncFormatter(format_date))
ax.set_xlabel(label)
fig.autofmt_xdate()
def DistVel2Time(distance, velocity_kph):
velocity_ms = velocity_kph / 3.6
time_sec = distance / velocity_ms
hours = int(time_sec//3600)
minutes = int((time_sec%3600)//60)
seconds = int(time_sec%60)
return "{:02d}:{:02d}".format(minutes, seconds)
times = [DistVel2Time(a, b) for a, b in [(5000, 13), (5000, 15), (5000, 14)]]
dates = [dt.datetime(year, month, day) for year, month, day in [(2019,2,1), (2019,2,2), (2019,2,7)]]
fig_1, ax_1 = plt.subplots()
ax_1.plot(dates, times, 'o--')
ax_1.xaxis_date()
ax_1.xaxis.set_major_formatter(mdates.DateFormatter('%d.%m.%Y'))
#ax_1.yaxis_date()
#ax_1.yaxis.set_major_formatter(mdates.DateFormatter("%M:%S"))
fig_1.autofmt_xdate()
plt.show()
fig_2, ax_2 = plt.subplots()
ax_2.plot(dates, times, 'D--')
ax_2.xaxis_date()
ax_2.xaxis.set_major_formatter(mdates.DateFormatter('%d.%m.%Y'))
equidate_ax(fig_2, ax_2, dates)
plt.show()
fig_1.savefig('fig1.png')
fig_2.savefig('fig2.png')
I stole the equidate_ax from #ascripter (from the second link) because I would like to skip all dates that I do not run.
If I run this piece of code, and save the figures, I end up getting the following two figures that are rather strange, as the y-axis does not distinguish between lower or higher values (Figures 1 and 2), and the x-axis for Figure 2 is repeating itself.
Figure 1: fig_1 from the code above.
Figure 2: fig_2 from the code above.
Why is not the y-axis plotting correctly in terms of lower or higher values?
How can I prevent the equidate_ax function from repeating itself and rather skip the unwanted dates?
If anyone could help cleaning up my mess, I would be grateful.
Combining the answers from the questions linked:
You basically have to make sure that matplotlib cannot guess the format of the x-axis but can guess the format of the y-axis.
With this matplotlib will not try to be smart and add dates you do not want to display on the x-axis but at the same time will be smart and sort the times for you on the y-axis.
from __future__ import division
from matplotlib import pyplot as plt
from matplotlib.ticker import FuncFormatter
import matplotlib.dates as mdates
import numpy as np
import datetime as dt
def DistVel2Time(distance, velocity_kph):
velocity_ms = velocity_kph / 3.6
time_sec = distance / velocity_ms
hours = int(time_sec//3600)
minutes = int((time_sec%3600)//60)
seconds = int(time_sec%60)
# note that I return a timedelta object here
return dt.timedelta(minutes=minutes, seconds=seconds)
# we have to choose a interpretable data-type here, simply take the total time needed in seconds
times = [ DistVel2Time(a, b).total_seconds() for a, b in [(5000, 13), (5000, 15), (5000, 14)]]
# here we want to make sure that matplotlib cannot interpret it so we use strings directly
# change the format as required
dates = [ "%00d.%00d.%000d" % ymd for ymd in [(2019,2,1), (2019,2,2), (2019,2,7)]]
# the formatting function taken from https://stackoverflow.com/questions/48294332/plot-datetime-timedelta-using-matplotlib-and-python
def format_func(x, pos):
hours = int(x//3600)
minutes = int((x%3600)//60)
seconds = int(x%60)
return "{:d}:{:02d}:{:02d}".format(hours, minutes, seconds)
formatter = FuncFormatter(format_func)
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.plot(dates, times, 'o--')
ax.yaxis.set_major_formatter(formatter)
plt.show()
It will produce a plot like this:
Although #milck answered my questions, I made a more streamlined version myself inspired by his answer and the previously mentioned answers from the question.
from matplotlib import pyplot as plt
from matplotlib.ticker import FuncFormatter
def DistVel2Time(*velocity_kph):
distance = 5000
times = [int(distance / (_ / 3.6)) for _ in velocity_kph]
return times
times = DistVel2Time(13, 15, 14)
dates = ["%00d.%00d.%000d" % dmy for dmy in [(1,2,2019), (2,2,2019), (7,2,2019)]]
def format_func(x, pos):
#hours = int(x//3600)
minutes = int((x%3600)//60)
seconds = int(x%60)
return "{:02d}:{:02d}".format(minutes, seconds)
formatter = FuncFormatter(format_func)
fig, ax = plt.subplots()
ax.plot(dates, times, 'D--')
ax.yaxis.set_major_formatter(formatter)
fig.autofmt_xdate()
plt.show()
This is shorter and perhaps easier to understand.
Related
I have time-series plots (over 1 year) where the months on the x-axis are of the form Jan, Feb, Mar, etc, but I would like to have just the first letter of the month instead (J,F,M, etc). I set the tick marks using
ax.xaxis.set_major_locator(MonthLocator())
ax.xaxis.set_minor_locator(MonthLocator())
ax.xaxis.set_major_formatter(matplotlib.ticker.NullFormatter())
ax.xaxis.set_minor_formatter(matplotlib.dates.DateFormatter('%b'))
Any help would be appreciated.
The following snippet based on the official example here works for me.
This uses a function based index formatter order to only return the first letter of the month as requested.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.mlab as mlab
import matplotlib.cbook as cbook
import matplotlib.ticker as ticker
datafile = cbook.get_sample_data('aapl.csv', asfileobj=False)
print 'loading', datafile
r = mlab.csv2rec(datafile)
r.sort()
r = r[-365:] # get the last year
# next we'll write a custom formatter
N = len(r)
ind = np.arange(N) # the evenly spaced plot indices
def format_date(x, pos=None):
thisind = np.clip(int(x+0.5), 0, N-1)
return r.date[thisind].strftime('%b')[0]
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(ind, r.adj_close, 'o-')
ax.xaxis.set_major_formatter(ticker.FuncFormatter(format_date))
fig.autofmt_xdate()
plt.show()
I tried to make the solution suggested by #Appleman1234 work, but since I, myself, wanted to create a solution that I could save in an external configuration script and import in other programs, I found it inconvenient that the formatter had to have variables defined outside of the formatter function itself.
I did not solve this but I just wanted to share my slightly shorter solution here so that you and maybe others can take it or leave it.
It turned out to be a little tricky to get the labels in the first place, since you need to draw the axes, before the tick labels are set. Otherwise you just get empty strings, when you use Text.get_text().
You may want to get rid of the agrument minor=True which was specific to my case.
# ...
# Manipulate tick labels
plt.draw()
ax.set_xticklabels(
[t.get_text()[0] for t in ax.get_xticklabels(minor=True)], minor=True
)
I hope it helps:)
The original answer uses the index of the dates. This is not necessary. One can instead get the month names from the DateFormatter('%b') and use a FuncFormatter to use only the first letter of the month.
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.ticker import FuncFormatter
from matplotlib.dates import MonthLocator, DateFormatter
x = np.arange("2019-01-01", "2019-12-31", dtype=np.datetime64)
y = np.random.rand(len(x))
fig, ax = plt.subplots()
ax.plot(x,y)
month_fmt = DateFormatter('%b')
def m_fmt(x, pos=None):
return month_fmt(x)[0]
ax.xaxis.set_major_locator(MonthLocator())
ax.xaxis.set_major_formatter(FuncFormatter(m_fmt))
plt.show()
I'm having trouble limiting the number of dates on the x-axis to make them legible. I need to plot the word length vs the year but the number of years is too large for the plot size.
The Issue:
Any help is appreciated.
As mentioned in the comments, use datetime (if your dates are in string format, you can easily convert them to datetime). Once you do that it should automatically display years along the x-axis. If you need to change the frequency of ticks to every year (or anything else), you can use mdates, like so:
import matplotlib.dates as mdates
import matplotlib.pyplot as plt
import datetime
import math
start = datetime.datetime.strptime("01-01-2000", "%d-%m-%Y")
end = datetime.datetime.strptime("10-04-2019", "%d-%m-%Y")
x = [start + datetime.timedelta(days=x) for x in range(0, (end-start).days)]
y = [math.sqrt(x) for x in range(len(x))]
fig, ax = plt.subplots()
ax.plot(x, y)
ax.xaxis.set_major_locator(mdates.YearLocator())
fig.autofmt_xdate()
plt.show()
The snippet above generates the following:
This code plots the data exactly as I want with the dates on the x-axis and the times on the y-axis. However I want the y-axis to show every hour on the hour (e.g., 00, 01, ... 23) and the x-axis to show the beginning of every month at an angle so there's no overlap (the actual data being used spans over a year) and only once, since this code repeats the same months. How is this accomplished?
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
data = ['2018-01-01 09:28:52', '2018-01-03 13:02:44', '2018-01-03 15:30:27', '2018-02-04 11:55:09']
f, ax = plt.subplots()
data = pd.to_datetime(data, yearfirst=True)
ax.plot(data.date, data.time, '.')
ax.set_ylim(["00:00:00", "23:59:59"])
days = mdates.DayLocator()
d_fmt = mdates.DateFormatter('%Y-%m')
ax.xaxis.set_major_locator(days)
ax.xaxis.set_major_formatter(d_fmt)
plt.show()
UPDATE: This fixes the x axis.
# Monthly intervals on x axis
months = mdates.MonthLocator()
d_fmt = mdates.DateFormatter('%Y-%m')
ax.xaxis.set_major_locator(months)
ax.xaxis.set_major_formatter(d_fmt)
However, this attempt to fix the y axis just makes it blank.
# Hourly intervals on y axis
hours = mdates.HourLocator()
t_fmt = mdates.DateFormatter('%H')
ax.yaxis.set_major_locator(hours)
ax.yaxis.set_major_formatter(t_fmt)
I'm reading these docs but not understanding my error: https://matplotlib.org/api/dates_api.html, https://matplotlib.org/api/ticker_api.html
Matplotlib cannot plot times without corresponding date. This would make is necessary to add some arbitrary date (in the below case I took the 1st of january 2018) to the times. One may use datetime.datetime.combine for that purpose.
timetodatetime = lambda x:dt.datetime.combine(dt.date(2018, 1, 1), x)
time = list(map(timetodatetime, data.time))
ax.plot(data.date, time, '.')
Then the code from the question using HourLocator() would work fine. Finally, setting the limits on the axes would also require to use datetime objects,
ax.set_ylim([dt.datetime(2018,1,1,0), dt.datetime(2018,1,2,0)])
Complete example:
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import datetime as dt
data = ['2018-01-01 09:28:52', '2018-01-03 13:02:44', '2018-01-03 15:30:27',
'2018-02-04 11:55:09']
f, ax = plt.subplots()
data = pd.to_datetime(data, yearfirst=True)
timetodatetime = lambda x:dt.datetime.combine(dt.date(2018, 1, 1), x)
time = list(map(timetodatetime, data.time))
ax.plot(data.date, time, '.')
# Monthly intervals on x axis
months = mdates.MonthLocator()
d_fmt = mdates.DateFormatter('%Y-%m')
ax.xaxis.set_major_locator(months)
ax.xaxis.set_major_formatter(d_fmt)
## Hourly intervals on y axis
hours = mdates.HourLocator()
t_fmt = mdates.DateFormatter('%H')
ax.yaxis.set_major_locator(hours)
ax.yaxis.set_major_formatter(t_fmt)
ax.set_ylim([dt.datetime(2018,1,1,0), dt.datetime(2018,1,2,0)])
plt.show()
If I run the following, it appears to work as expected, but the y-axis is limited to the earliest and latest times in the data. I want it to show midnight to midnight. I thought I could do that with the code that's commented out. But when I uncomment it, I get the correct y-axis, yet nothing plots. Where am I going wrong?
from datetime import datetime
import matplotlib.pyplot as plt
data = ['2018-01-01 09:28:52', '2018-01-03 13:02:44', '2018-01-03 15:30:27', '2018-01-04 11:55:09']
x = []
y = []
for i in range(0, len(data)):
t = datetime.strptime(data[i], '%Y-%m-%d %H:%M:%S')
x.append(t.strftime('%Y-%m-%d')) # X-axis = date
y.append(t.strftime('%H:%M:%S')) # Y-axis = time
plt.plot(x, y, '.')
# begin = datetime.strptime('00:00:00', '%H:%M:%S').strftime('%H:%M:%S')
# end = datetime.strptime('23:59:59', '%H:%M:%S').strftime('%H:%M:%S')
# plt.ylim(begin, end)
plt.show()
Edit: I also noticed that the x-axis isn't right either. The data skips Jan 2, but I want that on the axis so the data is to scale.
This is a dramatically simplified version of code dealing with over a year's worth of data with over 2,500 entries.
If Pandas is available to you, consider this approach:
import pandas as pd
data = pd.to_datetime(data, yearfirst=True)
plt.plot(data.date, data.time)
_=plt.ylim(["00:00:00", "23:59:59"])
Update per comments
X-axis date formatting can be adjusted using the Locator and Formatter methods of the matplotlib.dates module. Locator finds the tick positions, and Formatter specifies how you want the labels to appear.
Sometimes Matplotlib/Pandas just gets it right, other times you need to call out exactly what you want using these extra methods. In this case, I'm not sure why those numbers are showing up, but this code will remove them.
import pandas as pd
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
f, ax = plt.subplots()
data = pd.to_datetime(data, yearfirst=True)
ax.plot(data.date, data.time)
ax.set_ylim(["00:00:00", "23:59:59"])
days = mdates.DayLocator()
d_fmt = mdates.DateFormatter('%m-%d')
ax.xaxis.set_major_locator(days)
ax.xaxis.set_major_formatter(d_fmt)
All I want is quite straight forward, I just want the locator ticks to start at a specified timestamp:
peudo code: locator.set_start_ticking_at( datetime_dummy )
I have no luck finding anything so far.
Here is the portion of the code for this question:
axes[0].set_xlim(datetime_dummy) # datetime_dummy = '2015-12-25 05:34:00'
import matplotlib.dates as matdates
seclocator = matdates.SecondLocator(interval=20)
minlocator = matdates.MinuteLocator(interval=1)
hourlocator = matdates.HourLocator(interval=12)
seclocator.MAXTICKS = 40000
minlocator.MAXTICKS = 40000
hourlocator.MAXTICKS = 40000
majorFmt = matdates.DateFormatter('%Y-%m-%d, %H:%M:%S')
minorFmt = matdates.DateFormatter('%H:%M:%S')
axes[0].xaxis.set_major_locator(minlocator)
axes[0].xaxis.set_major_formatter(majorFmt)
plt.setp(axes[0].xaxis.get_majorticklabels(), rotation=90 )
axes[0].xaxis.set_minor_locator(seclocator)
axes[0].xaxis.set_minor_formatter(minorFmt)
plt.setp(axes[0].xaxis.get_minorticklabels(), rotation=90 )
# other codes
# save fig as a picture
The x axis ticks of above code will get me:
How do I tell the minor locator to align with the major locator?
How do I tell the locators which timestamp to start ticking at?
what I have tried:
set_xlim doesn't do the trick
seclocator.tick_values(datetime_dummy, datetime_dummy1) doesn't do anything
Instead of using the interval keyword parameter, use bysecond and byminute to specify exactly which seconds and minutes you with to mark. The bysecond and byminute parameters are used to construct a dateutil rrule. The rrule generates datetimes which match certain specified patterns (or, one might say, "rules").
For example, bysecond=[20, 40] limits the datetimes to those whose seconds
equal 20 or 40. Thus, below, the minor tick marks only appear for datetimes
whose soconds equal 20 or 40.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as matdates
N = 100
fig, ax = plt.subplots()
x = np.arange(N).astype('<i8').view('M8[s]').tolist()
y = (np.random.random(N)-0.5).cumsum()
ax.plot(x, y)
seclocator = matdates.SecondLocator(bysecond=[20, 40])
minlocator = matdates.MinuteLocator(byminute=range(60)) # range(60) is the default
seclocator.MAXTICKS = 40000
minlocator.MAXTICKS = 40000
majorFmt = matdates.DateFormatter('%Y-%m-%d, %H:%M:%S')
minorFmt = matdates.DateFormatter('%H:%M:%S')
ax.xaxis.set_major_locator(minlocator)
ax.xaxis.set_major_formatter(majorFmt)
plt.setp(ax.xaxis.get_majorticklabels(), rotation=90)
ax.xaxis.set_minor_locator(seclocator)
ax.xaxis.set_minor_formatter(minorFmt)
plt.setp(ax.xaxis.get_minorticklabels(), rotation=90)
plt.subplots_adjust(bottom=0.5)
plt.show()
#unutbu: Many thanks: I've been looking everywhere for the answer to a related problem!
#eliu: I've adapted unutbu's excellent answer to demonstrate how you can define lists (to create different 'dateutil' rules) which give you complete control over which x-ticks are displayed. Try un-commenting each example below in turn and play around with the values to see the effect. Hope this helps.
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
idx = pd.date_range('2017-01-01 05:03', '2017-01-01 18:03', freq = 'min')
df = pd.Series(np.random.randn(len(idx)), index = idx)
fig, ax = plt.subplots()
# Choose which major hour ticks are displayed by creating a 'dateutil' rule e.g.:
# Only use the hours in an explicit list:
# hourlocator = mdates.HourLocator(byhour=[6,12,8])
# Use the hours in a range defined by: Start, Stop, Step:
# hourlocator = mdates.HourLocator(byhour=range(8,15,2))
# Use every 3rd hour:
# hourlocator = mdates.HourLocator(interval = 3)
# Set the format of the major x-ticks:
majorFmt = mdates.DateFormatter('%H:%M')
ax.xaxis.set_major_locator(hourlocator)
ax.xaxis.set_major_formatter(majorFmt)
#... and ditto to set minor_locators and minor_formatters for minor x-ticks if needed as well)
ax.plot(df.index, df.values, color = 'black', linewidth = 0.4)
fig.autofmt_xdate() # optional: makes 30 deg tilt on tick labels
plt.show()