Inverse Discrete Cosine Transform
Compute the inverse unitary discrete cosine transform of a signal.
idct(x, n = NROW(x))
x |
input discrete cosine transform, specified as a numeric vector or matrix. In case of a vector it represents a single signal; in case of a matrix each column is a signal. |
n |
transform length, specified as a positive integer scalar. Default:
|
The discrete cosine transform (DCT) is closely related to the discrete Fourier transform. You can often reconstruct a sequence very accurately from only a few DCT coefficients. This property is useful for applications requiring data reduction.
Inverse discrete cosine transform, returned as a vector or matrix.
Paul Kienzle, pkienzle@users.sf.net.
Conversion to R by Geert van Boxtel, G.J.M.vanBoxtel@gmail.com.
x <- seq_len(100) + 50 * cos(seq_len(100) * 2 * pi / 40)
X <- dct(x)
# Find which cosine coefficients are significant (approx.)
# zero the rest
nsig <- which(abs(X) < 1)
N <- length(X) - length(nsig) + 1
X[nsig] <- 0
# Reconstruct the signal and compare it to the original signal.
xx <- idct(X)
plot(x, type = "l")
lines(xx, col = "red")
legend("bottomright", legend = c("Original", paste("Reconstructed, N =", N)),
lty = 1, col = 1:2)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.