How To Add A Line To A Contour Plot Python
20. Profile Plots with Matplotlib
By Bernd Klein. Terminal modified: 01 Feb 2022.
Contour Plot
A contour line or isoline of a function of ii variables is a curve along which the function has a constant value.
It is a cross-section of the 3-dimensional graph of the office f(x, y) parallel to the x, y aeroplane.
Profile lines are used e.g. in geography and meteorology.
In cartography, a profile line joins points of equal tiptop (height) above a given level, such as hateful sea level.
We can also say in a more full general way that a contour line of a function with ii variables is a curve which connects points with the same values.
Creating a "meshgrid"
# the following line is only necessary if working with "ipython notebook" % matplotlib inline import matplotlib.pyplot as plt import numpy every bit np north , m = 7 , vii start = - 3 x_vals = np . arange ( starting time , commencement + n , one ) y_vals = np . arange ( start , start + chiliad , i ) 10 , Y = np . meshgrid ( x_vals , y_vals ) print ( X ) impress ( Y ) OUTPUT:
[[-3 -two -one 0 ane 2 3] [-3 -2 -1 0 1 2 3] [-3 -two -one 0 1 2 iii] [-3 -2 -1 0 one ii 3] [-three -two -1 0 ane 2 three] [-3 -2 -1 0 1 2 3] [-iii -ii -1 0 1 2 three]] [[-iii -3 -three -3 -3 -three -3] [-two -2 -ii -two -ii -2 -2] [-one -i -i -1 -1 -i -i] [ 0 0 0 0 0 0 0] [ 1 1 one ane 1 1 one] [ 2 2 2 2 2 2 2] [ 3 3 three iii 3 3 iii]]
We can visulize our meshgridif nosotros add the following code to our previous programme:
fig , ax = plt . subplots () ax . scatter ( X , Y , color = "green" ) ax . set_title ( 'Regular Filigree, created by Meshgrid' ) ax . set_xlabel ( 'x' ) ax . set_ylabel ( 'y' ) plt . show () 
import numpy equally np xlist = np . linspace ( - 3.0 , 3.0 , iii ) ylist = np . linspace ( - iii.0 , 3.0 , 4 ) X , Y = np . meshgrid ( xlist , ylist ) Z = np . sqrt ( X ** 2 + Y ** 2 ) print ( Z ) OUTPUT:
[[4.24264069 3. four.24264069] [3.16227766 1. 3.16227766] [iii.16227766 1. iii.16227766] [four.24264069 3. 4.24264069]]
Calculation of the Values
import numpy as np xlist = np . linspace ( - three.0 , 3.0 , 3 ) ylist = np . linspace ( - 3.0 , iii.0 , iv ) X , Y = np . meshgrid ( xlist , ylist ) Z = np . sqrt ( Ten ** 2 + Y ** 2 ) impress ( Z ) OUTPUT:
[[iv.24264069 3. 4.24264069] [three.16227766 1. iii.16227766] [three.16227766 1. 3.16227766] [iv.24264069 3. iv.24264069]]
fig = plt . effigy ( figsize = ( 6 , 5 )) left , bottom , width , height = 0.1 , 0.1 , 0.8 , 0.8 ax = fig . add_axes ([ left , lesser , width , summit ]) Z = np . sqrt ( Ten ** two + Y ** two ) cp = ax . contour ( X , Y , Z ) ax . clabel ( cp , inline = True , fontsize = x ) ax . set_title ( 'Contour Plot' ) ax . set_xlabel ( '10 (cm)' ) ax . set_ylabel ( 'y (cm)' ) plt . prove () 
Changing the Colours and the Line Manner
import matplotlib.pyplot every bit plt plt . figure () cp = plt . contour ( X , Y , Z , colors = 'black' , linestyles = 'dashed' ) plt . clabel ( cp , inline = True , fontsize = ten ) plt . title ( 'Contour Plot' ) plt . xlabel ( 'x (cm)' ) plt . ylabel ( 'y (cm)' ) plt . prove () 
Filled Contours
import matplotlib.pyplot as plt import numpy as np fig = plt . figure ( figsize = ( 6 , 5 )) left , bottom , width , height = 0.1 , 0.ane , 0.8 , 0.8 ax = fig . add_axes ([ left , bottom , width , tiptop ]) start , cease , n_values = - viii , 8 , 800 x_vals = np . linspace ( start , stop , n_values ) y_vals = np . linspace ( start , stop , n_values ) X , Y = np . meshgrid ( x_vals , y_vals ) Z = np . sqrt ( X ** 2 + Y ** 2 ) cp = plt . contourf ( X , Y , Z ) plt . colorbar ( cp ) ax . set_title ( 'Contour Plot' ) ax . set_xlabel ( 'ten (cm)' ) ax . set_ylabel ( 'y (cm)' ) plt . show () 
Private Colours
import numpy as np import matplotlib.pyplot as plt xlist = np . linspace ( - 3.0 , 3.0 , 100 ) ylist = np . linspace ( - three.0 , three.0 , 100 ) 10 , Y = np . meshgrid ( xlist , ylist ) Z = np . sqrt ( X ** 2 + Y ** 2 ) plt . effigy () profile = plt . profile ( X , Y , Z ) plt . clabel ( contour , colors = 'yard' , fmt = ' %2.1f ' , fontsize = 12 ) c = ( '#ff0000' , '#ffff00' , '#0000FF' , '0.6' , 'c' , 'thou' ) contour_filled = plt . contourf ( Ten , Y , Z , colors = c ) plt . colorbar ( contour_filled ) plt . title ( 'Filled Contours Plot' ) plt . xlabel ( 'x (cm)' ) plt . ylabel ( 'y (cm)' ) plt . savefig ( 'contourplot_own_colours.png' , dpi = 300 ) plt . testify () 
Levels
The levels were decided automatically by contour and contourf and then far. They tin can be defined manually, by providing a list of levels equally a fourth parameter. Contour lines will exist fatigued for each value in the list, if we use contour. For contourf, at that place will be filled colored regions between the values in the list.
import numpy every bit np import matplotlib.pyplot every bit plt xlist = np . linspace ( - 3.0 , three.0 , 100 ) ylist = np . linspace ( - 3.0 , three.0 , 100 ) X , Y = np . meshgrid ( xlist , ylist ) Z = np . sqrt ( X ** 2 + Y ** ii ) plt . effigy () levels = [ 0.0 , 0.two , 0.five , 0.9 , 1.5 , 2.5 , 3.5 ] contour = plt . contour ( X , Y , Z , levels , colors = 'k' ) plt . clabel ( profile , colors = 'k' , fmt = ' %two.1f ' , fontsize = 12 ) contour_filled = plt . contourf ( X , Y , Z , levels ) plt . colorbar ( contour_filled ) plt . championship ( 'Plot from level list' ) plt . xlabel ( 'x (cm)' ) plt . ylabel ( 'y (cm)' ) plt . show ()
The terminal example of this chapter volition exist a "lovely" contour plot:
import matplotlib.pyplot as plt import numpy as np y , x = np . ogrid [ - one : 2 : 100 j , - ane : 1 : 100 j ] plt . contour ( x . ravel (), y . ravel (), x ** ii + ( y - (( x ** ii ) ** ( 1.0 / 3 ))) ** ii , [ one ], colors = 'red' ,) plt . axis ( 'equal' ) plt . testify ()
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How To Add A Line To A Contour Plot Python,
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