minimum value of y axis is not being applied in matplotlib vlines plot
You can set the limit manually after plotting the data, like so:
pyplot.ylim(ymin=0)
What happens is that Matplotlib adjusts the plot limits so that it looks "best". Sometimes, this implies going beyond the strict range of your data. You must then update the limits after the plot, since each plot updates the limit (if I understand correctly).
Now, your approach can work, but you must update the figure after setting the limits:
ax.set_ylim(bottom=0)
pylot.draw()
(This works in the IPython shell on Mac OS X with the latest version of matplotlib.)
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sharat87
Updated on April 05, 2020Comments
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sharat87 almost 4 years
I am doing a vlines plot in matplotlib and I have all my y values in the dataset as
>=0
. I want my y axis bottom most tick to read0
, but instead, I get -500.Here is the code:
#!/usr/bin/env python import numpy as np from matplotlib import pyplot as plt, dates as mdates import datetime as dt, time # Read the data and turn it into a numpy array #store = map(lambda line: map(int, line.strip().split()), open(name + '.txt').readlines()) store = [ [1293606162197, 0, 0], [1293605477994, 63, 0], [1293605478057, 0, 0], [1293605478072, 2735, 1249], [1293606162213, 0, 0], [1293606162229, 0, 0], ] nstore = np.array(store) # Get arrays of each columns in the store array d = nstore[:,0] y1 = nstore[:,1] y2 = nstore[:,2] # Get arrays of values to be passed to matplotlib s = d / 1000 dts = map(dt.datetime.fromtimestamp, s) fds = mdates.date2num(dts) # new figure and subplot fig = plt.figure() ax = fig.add_subplot(111) # Plot using vlines ax.vlines(fds, [0], y1, 'red') # set xaxis tick settings ax.xaxis.set_major_locator(mdates.MinuteLocator()) ax.xaxis.set_major_formatter(mdates.DateFormatter('%m/%d %H:%M')) for label in ax.xaxis.get_ticklabels(): label.set_rotation('vertical') fig.subplots_adjust(bottom=.25) # Set the y axis bottom limit to 0 ax.set_ylim(bottom=0) # <<- THIS DOES NOT SEEM TO BE WORKING # Save the plot figure fig.savefig('out.png')
and here is the plot I get:
Can anyone point to me what I am doing wrong? Also, if you can point me to the docs that have the details I need, that would be great. Thanks.
Question is a follow up of Creating graph with date and time in axis labels with matplotlib
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sharat87 almost 13 yearsah, thanks EOL, that gets it working. Is there an equivalent of this method in an object oriented style, as I will be doing many plots in parallel.
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Bruno Feroleto almost 13 years@Shrikant: I added an object-oriented approach to my answer.
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sharat87 almost 13 yearsI get a
TypeError: draw_wrapper() takes at least 2 arguments (1 given)
withax.draw()
, running on Ubuntu. -
Bruno Feroleto almost 13 years@Shrikant: Sorry; I updated the answer with the correct call to
draw()
. -
sharat87 almost 13 yearsOh boy! I got it figured, changing
ax.set_ylim(bottom=0)
toax.set_ylim(ymin=0)
works like a charm, without the need for a call to.draw()
. Thanks -
sharat87 almost 13 yearsright, my
matplotlib.__version__
spits out0.99.3
, the latest version on the website seems to be1.0.1
, damn ubuntu repos! -
Bruno Feroleto almost 13 years@Shrikant: Interesting but strange:
ax.set_ylim(ymin=…)
does not update the graph on my Mac OS X (through IPython) andpyplot.draw()
is stil needed, like withbottom=…
. It may therefore be better to consistently use portable code and include thedraw()
. :) -
Bruno Feroleto about 9 yearsFor the record:
ax.set_ylim(ymin=…)
is old syntax and is obsoleted by thebottom=…
of the answer.