[CodeStudy] Python Matplotlib
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by
SingularityKChen
(Last updated:
)
- Categories:
- CodeStudy 12
- Tags:
- Matplotlib 2
- Python 5
Python Matplotlib
Basic Operations
# import the lib
import matplotlib.pyplot as plt
# create your figure
my_fig = plt.figure()
# add your sub plot and draw graph here
# let's assume we need a 2 x 2 graph
my_sub_plot_1 = my_fig.add_subplot(2, 2, 1)
my_sub_plot_2 = my_fig.add_subplot(2, 2, 2)
my_sub_plot_3 = my_fig.add_subplot(2, 2, 3)
my_sub_plot_4 = my_fig.add_subplot(2, 2, 4)
# now plot the dots and lines
a = ...
b = ...
my_sub_plot_1.plot(a, b)
...
# then show the graph
plt.show()
You can change the number of sub plots, just modify the parameters in add_subplot().
And you can also combine the subplot operation by:
my_fig, (my_sub_plot_1, my_sub_plot_2, my_sub_plot_3, my_sub_plot_4 = plt.subplots(nrows=2, ncols=2)
Which I think is much better.
Transfer Subplots into a function and plot it
If you want to send the graph to a function and return it to the main function after adding some details in the graph, you can not send the Figure object otherwise you'll meet this error:
AttributeError: 'Figure' object has no attribute 'plot'
In this case, you can not send the variable my_fig into the function, but you can send the sub plot into the function and return it.
def my_func:(f_plot):
a = ...
b = ...
f_plot.plot(a, b)
return f_plot
However, I suggest just append the list out and plot them at one time, which is much faster in my case.
Useful format to custom your lines
The syntax of plot is:
plot([x], [y], [format], [x2], y2, [format2], ..., **kwargs)
Where the format including color, markers, line style. You can even add more parameters like
plot(x,y2,color='green', marker='o', linestyle='dashed', linewidth=1, markersize=6)
plot(x,y3,color='#900302',marker='+',linestyle='-')
Here is a reference of characters1 that you can use like
plot(x, y, 'bo-')
**Markers**
============= ===============================
character description
============= ===============================
``'.'`` point marker
``','`` pixel marker
``'o'`` circle marker
``'v'`` triangle_down marker
``'^'`` triangle_up marker
``'<'`` triangle_left marker
``'>'`` triangle_right marker
``'1'`` tri_down marker
``'2'`` tri_up marker
``'3'`` tri_left marker
``'4'`` tri_right marker
``'s'`` square marker
``'p'`` pentagon marker
``'*'`` star marker
``'h'`` hexagon1 marker
``'H'`` hexagon2 marker
``'+'`` plus marker
``'x'`` x marker
``'D'`` diamond marker
``'d'`` thin_diamond marker
``'|'`` vline marker
``'_'`` hline marker
============= ===============================
**Line Styles**
============= ===============================
character description
============= ===============================
``'-'`` solid line style
``'--'`` dashed line style
``'-.'`` dash-dot line style
``':'`` dotted line style
============= ===============================
Example format strings::
'b' # blue markers with default shape
'or' # red circles
'-g' # green solid line
'--' # dashed line with default color
'^k:' # black triangle_up markers connected by a dotted line
**Colors**
The supported color abbreviations are the single letter codes
============= ===============================
character color
============= ===============================
``'b'`` blue
``'g'`` green
``'r'`` red
``'c'`` cyan
``'m'`` magenta
``'y'`` yellow
``'k'`` black
``'w'`` white
============= ===============================
Plot shapes and plot from Data Frames
For this part, you can see this post1.