How to plot the integral of a signal as time goes by?

Question

I have a time-dependent signal.

I wish to plot its integration over time with time being x-axis and integration value being y-axis.

Is there any Python way of doing this?

To be more specific:

I have a time array, time, and a signal array, signal. They are of same dimension.

I need to integrate signal over time with scipy.integrate.trapz().

Instead of getting the final integral, I wish to see the integral varying as time passes.

Answer 1

Try using scipy.integrate.cumtrapz() instead :

plt.plot(time[:-1], scipy.integrate.cumtrapz(signal, x=time))
plt.show()

It computes an array containing the cumulative integral values.

http://docs.scipy.org/doc/scipy-0.10.1/reference/generated/scipy.integrate.trapz.html

Answer 2

A slightly better answer uses the optional "initial" argument. Here is a complete example:

import scipy.integrate as it
import numpy as np 
import matplotlib.pyplot as plt
t=np.linspace(0,1, 100)
y=t**2
y_int = it.cumtrapz(  y  ,  t, initial=0.0)  # y_int is same size as t
plt.plot(t, y_int)
plt.show()

This avoids the strange indexing like time[:-1]