Matplotlib 3.0 Cookbook
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Reading from a .txt file

Here are some steps to follow:

  1. Read the text file into the txt variable:
txt = np.loadtxt('test.txt', delimiter = ',')
txt

Here is the explanation for the preceding code block:

  • The test.txt text file has 10 numbers separated by a comma, representing the x and y coordinates of five points (1, 1), (2, 4), (3, 9), (4, 16), and (5, 25) in a two-dimensional space.
  • The loadtxt() function loads text data into a NumPy array.

You should get the following output:

array([ 1., 1., 2., 4., 3., 9., 4., 16., 5., 25.])
  1. Convert the flat array into five points in 2D space:
txt = txt.reshape(5,2)
txt

After executing preceding code, you should see the following output:

array([[ 1., 1.], [ 2., 4.], [ 3., 9.], [ 4., 16.], [ 5., 25.]])
  1. Split the .txt variable into x and y axis co-ordinates:
x = txt[:,0]
y = txt[:,1]
print(x, y)

Here is the explanation for the preceding code block:

  • Separate the x and y axis points from the txt variable.
  • x is the first column in txt and y is the second column.
  • The Python indexing starts from 0.

After executing the preceding code, you should see the following output:

[ 1. 2. 3. 4. 5.] [ 1. 4. 9. 16. 25.]