Intersection of two graphs in Python, find the x value

by

You can use np.sign in combination with np.diff and np.argwhere to obtain the indices of points where the lines cross (in this case, the points are [ 0, 149, 331, 448, 664, 743]):

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 1000)
f = np.arange(0, 1000)
g = np.sin(np.arange(0, 10, 0.01) * 2) * 1000

plt.plot(x, f, '-')
plt.plot(x, g, '-')

idx = np.argwhere(np.diff(np.sign(f - g))).flatten()
plt.plot(x[idx], f[idx], 'ro')
plt.show()

plot of intersection points

First it calculates f - g and the corresponding signs using np.sign. Applying np.diff reveals all the positions, where the sign changes (e.g. the lines cross). Using np.argwhere gives us the exact indices.

More Related Contents:

  1. How to find the intersection of two graphs
  2. Dynamically updating plot in matplotlib
  3. Is there a way to detach matplotlib plots so that the computation can continue?
  4. python matplotlib update scatter plot from a function
  5. how do I make a single legend for many subplots with matplotlib?
  6. Matplotlib – label each bin
  7. Defining the midpoint of a colormap in matplotlib
  8. How do I fit a sine curve to my data with pylab and numpy?
  9. Using Colormaps to set color of line in matplotlib
  10. Python – Legend overlaps with the pie chart
  11. warning about too many open figures
  12. Add alpha to an existing matplotlib colormap
  13. Sans-serif math with latex in matplotlib
  14. tight_layout() doesn’t take into account figure suptitle
  15. How to remove or hide x-axis labels from a seaborn / matplotlib plot
  16. python matplotlib blit to axes or sides of the figure?
  17. Colorbar for matplotlib plot_surface command
  18. plot decision boundary matplotlib
  19. Large Dataset Polynomial Fitting Using Numpy
  20. How to add a string as the artist in matplotlib legend?
  21. Plot a bar plot from a Pandas DataFrame
  22. Python Scatter Plot with Multiple Y values for each X
  23. How to skip empty dates (weekends) in a financial Matplotlib Python graph?
  24. Matplotlib: How to colorize a large number of line segments as independent gradients, efficiently
  25. How to create major and minor gridlines with different linestyles in Python
  26. How to increase the space between bar plot bars
  27. Intersection of two pandas dataframes based on column entries
  28. Matplotlib move tick labels inside plot area
  29. Multiple datasets on the same scatter plot
  30. Create a figure that is reference counted

Leave a Comment