Any discrete finite wavelet transform can be represented as a matrix, and such a wavelet matrix
can be computed in 
steps, compared to 
for the Fourier matrix, where 
is the base-2 logarithm.
A single wavelet matrix can be built using Haar functions.
Wavelet Matrix
See also
Fourier Matrix, Haar Function, Wavelet, Wavelet TransformExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Wavelet Matrix." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/WaveletMatrix.html