Inverse Fast Walsh–Hadamard transform
y = ifwht(x)
y = ifwht(x,n)
y = ifwht(x,n,ordering)
y = ifwht(x) returns the coefficients of the inverse discrete fast Walsh–Hadamard transform of the input x. If x is a matrix, the inverse fast Walsh-Hadamard tranform is calculated on each column of x. The inverse fast Walsh-Hadamard tranform operates only on signals with length equal to a power of 2. If the length of x is less than a power of 2, its length is padded with zeros to the next greater power of two before processing.
y = ifwht(x,n) returns the n-point inverse discrete Walsh–Hadamard transform, where n must be a power of 2.
y = ifwht(x,n,ordering) specifies the ordering to use for the returned inverse Walsh–Hadamard transform coefficients. To specify ordering, you must enter a value for the length n or, to use the default behavior, specify an empty vector  for n. Valid values for ordering are the following strings:
|'sequency'||Coefficients in order of ascending sequency value, where each row has an additional zero crossing. This is the default ordering.|
|'hadamard'||Coefficients in normal Hadamard order.|
|'dyadic'||Coefficients in Gray code order, where a single bit change occurs from one coefficient to the next.|
 Beauchamp, K.G., Applications of Walsh and Related Functions, Academic Press, 1984.
 Beer, T., Walsh Transforms, American Journal of Physics, Volume 49, Issue 5, May 1981.