Matplotlib notes: contour & Contour

contour and contourf Draw contour lines and fill contour lines respectively

1 Basic usage

matplotlib.pyplot.contourf([X, Y,] Z, [levels], **kwargs)

2 main parameter  

X, Y	Z Coordinates of values in . X and Y Must be two-dimensional , Have and Z The same shape （ for example , adopt numpy.meshgrid establish ）, Or they must all be one-dimensional , such len(X) == N ,len(Y ) == M yes Z The number of rows and columns in . X and Y Must be sorted monotonically .
z	Draw the height value of the contour line .
levels	Determine contour lines / Number and location of areas . If it's an integer n, Please use MaxNLocator, It will try to vmin and vmax No more than... Are automatically selected between n+1 individual ” good “ At the same high level . If it's an array , Contour lines are drawn at the specified level . These values must be arranged in ascending order .
colors	Color of level , That is, contour lines and contour areas . This sequence loops through the levels in ascending order . If the sequence is shorter than the number of levels , Then repeat . As a shortcut , You can use a single color string instead of a single element list , namely “red” instead of [“red”] Color all levels with the same color . By default （ value None）, Will use cmap Specified color map .
cmap
alpha	transparency ,0~1 Number between
extend	Determines the outline shading of values outside the level range . If “both”, Values outside the level range are not shaded . If it is “min”、“max” or “both”, Is less than 、 Values above or below and above the horizontal range are shaded . lower than min(levels) And above max(levels) The value of is mapped to the lower than of the color map / Above value .

 3 give an example

3.0 Data section

import numpy as np
import matplotlib.pyplot as plt
x = np.arange(1, 10)
y = x.reshape(-1, 1)
h = x * y
print(x,'\n',y,'\n',h)
'''
[1 2 3 4 5 6 7 8 9] 

 [[1]
 [2]
 [3]
 [4]
 [5]
 [6]
 [7]
 [8]
 [9]] 

 [[ 1  2  3  4  5  6  7  8  9]
 [ 2  4  6  8 10 12 14 16 18]
 [ 3  6  9 12 15 18 21 24 27]
 [ 4  8 12 16 20 24 28 32 36]
 [ 5 10 15 20 25 30 35 40 45]
 [ 6 12 18 24 30 36 42 48 54]
 [ 7 14 21 28 35 42 49 56 63]
 [ 8 16 24 32 40 48 56 64 72]
 [ 9 18 27 36 45 54 63 72 81]]
'''

3.1 The most basic

plt.contourf(x.reshape(-1),
             y.reshape(-1),
             h)

3.2 level 

plt.contourf(x.reshape(-1),
             y.reshape(-1),
             h,
             levels=1)

plt.contourf(x.reshape(-1),
             y.reshape(-1),
             h,
             levels=[1,3,15,35])

 3.3 extend

plt.contourf(x.reshape(-1),
             y.reshape(-1),
             h,
             levels=[13,15,35], 
             )

 

 

plt.contourf(x.reshape(-1),
             y.reshape(-1),
             h,
             levels=[13,15,35], 
             extend='both')