Inverse Discrete Cosine Transform

inverse_discrete_cosine_transform.py

#http://www.svcl.ucsd.edu/courses/ece161c/handouts/DCT.pdf

import numpy as np
import matplotlib.pyplot as plt

pi = np.pi

N = 50 # timesteps
k = 10 # n basis functions

coefs = np.random.rand(k) #generate random coeficients
ns = np.tile(np.arange(0, N, 1).reshape([N, 1]), [1, k])
coefs = np.tile(coefs.reshape([1, k]), [N, 1])
ks = np.tile(np.arange(0, k), [N, 1])

out = 1/N * np.sum(coefs *np.cos( (pi * ks * (2*ns + 1)) / (2*N)), axis=1)

plt.plot(ns[:, 0], out)