.Wavelet.Transform.idwt

Information

This function calculates inverse discrete wavelet transform (one-level wavelet reconstruction) using the input approximation and detail wavelet coefficients, ca and cd. The coefficient vectors are extended at both ends with zero padding before calculation. The length of the reconstructed data is usually (but not always) equal to the length of the original signal if the length is not specified.

Refer to the section of wavelet Families for the detailed information about the available wavelets.

The default input values provide a quick example to generate a simple saw-tooth signal.

Interface

function idwt
  input Real ca[:] = {2.121, 2.121, 2.121, 4.95, 0.707} "Approximation coefficients";
  input Real cd[size(ca, 1)] = {-0.707, -0.707, -0.707, -0.707, 0.707} "Detail coefficients";
  input Real lor[:] = {0.707, 0.707} "Low pass filter for reconstruction";
  input Real hir[size(lor, 1)] = {0.707, -0.707} "High pass filter for reconstruction";
  input Integer ny = 0 "Length of the result, y (the central part will be extracted). If ny == 0, size(y,1) = 2*size(ca,1) - size(lor,1) +2";
  output Real y[:] "Reconstructed signal";
end idwt;