Convolution vs Correlation Example

conv_test.py

#simple correlation vs convolution example
import numpy as np
from matplotlib.pyplot import *

style.use('seaborn-ticks')
for a in [[1,2,3],[1,2,1]]:
    figure()
    x=[-1,0,1]
    b = [0,0,1]

    avb = np.convolve(a,b,mode='full')
    bva = np.convolve(b,a,mode='full')
    arb = np.correlate(a,b,mode='full')
    bra = np.correlate(b,a,mode='full')
    names = ['signal a','signal b','a CONV b', 'b CONV a', 'a CORR b', 'b CORR a']
    for idx, value in enumerate([a,b,avb,bva,arb,bra]):
        subplot(3,2,idx+1)
        if idx > 1:
            x =[-2,-1,0,1,2]
        vlines(x,[0]*5,value,lw=5)
        xlim(-3,3)
        ylim(0,4)
        title(names[idx])
    tight_layout(pad=0.4, w_pad=0.5, h_pad=1.0)
show()