2D Graphics in Sage -- Matlab style

Sage also fully supports a library called matplotlib, which has an interface closely inspired by MATLAB™.

Many Pylab examples...

%auto
import numpy as np
import matplotlib.pyplot as plt

plt.plot([1,2,3], [4,5,7], )
plt.show()

[<matplotlib.lines.Line2D object at 0x7fb7319c9390>]

# We put the code from the example in a function, to avoid printing intermediate results.

def example():
    def f(t):
        return np.exp(-t) * np.cos(2*np.pi*t)

    t1 = np.arange(0.0, 5.0, 0.1)
    t2 = np.arange(0.0, 5.0, 0.02)

    plt.figure(1)
    plt.subplot(211)
    plt.plot(t1, f(t1), 'bo', t2, f(t2), 'k')

    plt.subplot(212)
    plt.plot(t2, np.cos(2*np.pi*t2), 'r--')
    plt.show()

# Now draw the plot.
example()

Copy and paste something below. You can highlight a block, then hit tab to indent the whole thing at once...


def example():
    t = np.arange(0.0, 2.0, 0.01)
    s = np.sin(2*np.pi*t)

    plt.plot(t,s)
    plt.title(r'$\alpha_i > \beta_i$', fontsize=20)
    plt.text(1, -0.6, r'$\sum_{i=0}^\infty\,\, x_i$', fontsize=20)
    plt.text(0.6, 0.6, r'$\mathcal{A}\mathrm{sin}(2 \omega t)$',
             fontsize=20)
    plt.xlabel('time (s)')
    plt.ylabel('volts (mV)')
    plt.show()

example()

You can also just directly use Octave, which is a MATLAB clone.

Use %plot -f svg to set octave to use nice looking SVG graphics.

%octave
%plot -f svg -s 800,600
plot([1,2,3], [4,5,7])
set(gca, "fontsize", 16)

%octave
x = 0:0.01:20;
y = (1 + sqrt(x)) .* sin (x);
plot (x, y);
set(gca, "fontsize", 16);
xlabel ("x");
ylabel ("(1 + sqrt(x)) * sin (x)");
title ("Simple 2-D Plot");



import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111, polar=True)
r = np.arange(0,1,0.001)
theta = 2 * 2*np.pi * r
line, = ax.plot(theta, r, color='#ee8d18', lw=3)

ind = 800
thisr, thistheta = r[ind], theta[ind]
ax.plot([thistheta], [thisr], 'o')
ax.annotate('a polar annotation',
            xy=(thistheta, thisr),  # theta, radius
            xytext=(0.05, 0.05),    # fraction, fraction
            textcoords='figure fraction',
            arrowprops=dict(facecolor='black', shrink=0.05),
            horizontalalignment='left',
            verticalalignment='bottom',
            )
plt.show()

[<matplotlib.lines.Line2D object at 0x7fb7318d1590>]
<matplotlib.text.Annotation object at 0x7fb7318d1850>