Plotting Coordinate Lines Using Matplotlib

Question

I want to plot the co-ordinate lines of a co-ordinate system (e.g. Cartesian co-ords) using matplotlib.

Then I want to transform them using some linear transform (skew, scale, rotate, etc.), and I want to plot this transformed version of the system as well.

I am quite new to matplotlib and I have no idea as to how I could go about doing this. Any suggestions?

Something like this:

Doesn't have to be on the same plot as above, I just want to be able to plot the lines (and shapes and their transformed versions as well).

EDIT: If you instead have a MATLAB solution, I'll take that too.

Do you have any code so far? Do you want the actual plot axes to be displayed with a linear transform (more complicated) or just plot the transformed objects on the normal plot (easy, just apply the appropriate mathematical formula to the points)? — user812786
– user812786, Commented Aug 18, 2016 at 13:15
I want a grid of coordinate lines as well. I want to show how the 'space' is transformed. — Silver
– Silver, Commented Aug 18, 2016 at 13:17

Community · Accepted Answer · 2017-05-23 12:33:02Z

1

user2539738's answer demonstrates how to draw a grid in a plot. The next step is applying a transform. This is a mathematical operation which can be described as a function of the x and y coordinates. For example, a shear transform like your example images -

def my_transform(x, y):
    return (x+y/2, y)

With this in mind, you can plot the transformed grid. You simply have to calculate the new coordinates:

# Transformed grid
for x in xx:
    (x1, y1) = my_transform(x, min(yy))
    (x2, y2) = my_transform(x, max(yy))
    plt.plot([x1,x2],[y1,y2],color='r')
for y in yy:
    (x1, y1) = my_transform(min(xx), y)
    (x2, y2) = my_transform(max(xx), y)
    plt.plot([x1,x2],[y1,y2],color='r')

This plots the transformed grid in red. The first for loop plots what were the vertical lines of the grid (going from point x, min(yy) to x, max(yy)), and the second plots the horizontal lines. The transform function is applied to the original pairs of points to calculate the new endpoints of the transformed line.

edited May 23, 2017 at 12:33

CommunityBot

11 silver badge

answered Aug 18, 2016 at 14:25

user812786

4,4306 gold badges42 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Silver Over a year ago

Thanks a lot! This is perfect.

Mohammad Athar · Accepted Answer · 2016-08-18 13:26:09Z

1

This should get you started on the right track

import matplotlib

import matplotlib.pyplot as plt

xx = range(10)
yy = range(10)
[plt.plot([x,x],[min(yy),max(yy)],color='k') for x in xx]
[plt.plot([min(xx),max(xx)],[y,y],color='k') for y in yy]

answered Aug 18, 2016 at 13:26

Mohammad Athar

1,9802 gold badges15 silver badges36 bronze badges

Collectives™ on Stack Overflow

Plotting Coordinate Lines Using Matplotlib

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related