# Fit a line, ``y = mx + c``, through some noisy data-points:

x = np.array([0, 1, 2, 3])
y = np.array([-1, 0.2, 0.9, 2.1])

# By examining the coefficients, we see that the line should have a
# gradient of roughly 1 and cut the y-axis at, more or less, -1.

# We can rewrite the line equation as ``y = Ap``, where ``A = [[x 1]]``
# and ``p = [[m], [c]]``.  Now use `lstsq` to solve for `p`:

A = np.vstack([x, np.ones(len(x))]).T
A
# array([[ 0.,  1.],
# [ 1.,  1.],
# [ 2.,  1.],
# [ 3.,  1.]])

m, c = np.linalg.lstsq(A, y)[0]
print m, c
# 1.0 -0.95

# Plot the data along with the fitted line:

import matplotlib.pyplot as plt
plt.plot(x, y, 'o', label='Original data', markersize=10)
plt.plot(x, m*x + c, 'r', label='Fitted line')
plt.legend()
plt.show()