Dyadic downsampling
Y = dyaddown(X,EVENODD)
Y = dyaddown(X)
Y = dyaddown(X,EVENODD,'type')
Y
= dyaddown(X,'type',EVENODD)
Y = dyaddown(X)
Y = dyaddown(X,'type')
Y = dyaddown(X,0,'type')
Y = dyaddown(X,EVENODD)
Y = dyaddown(X,EVENODD,'c')
Y = dyaddown(X,EVENODD) where X is
a vector, returns a version of X that
has been downsampled by 2. Whether Y contains the
even- or odd-indexed samples of X depends
on the value of positive integer EVENODD:
If EVENODD is even, then Y(k)
= X(2k).
If EVENODD is odd, then Y(k) = X(2k+1).
Y = dyaddown(X) is equivalent to Y
= dyaddown(X,0) (even-indexed samples).
Y = dyaddown(X,EVENODD, or 'type')Y
= dyaddown(X,,
where 'type',EVENODD)X is a matrix,
returns a version of X obtained by suppressing
one out of two:
Columns of | If |
Rows of | If |
Rows and columns of | If |
according to the parameter EVENODD,
which is as above.
If you omit the EVENODD or 'type'
arguments, dyaddown defaults to EVENODD = 0
(even-indexed samples) and 'type'= 'c'
(columns).
Y = dyaddown(X) is equivalent to Y
= dyaddown(X,0,'c').
Y = dyaddown(X, is
equivalent to 'type')Y = dyaddown(X,0,. 'type')
Y = dyaddown(X,EVENODD) is equivalent
to Y = dyaddown(X,EVENODD,'c').
% For a vector.
s = 1:10
s =
1 2 3 4 5 6 7 8 9 10
dse = dyaddown(s) % Downsample elements with even indices.
dse =
2 4 6 8 10
% or equivalently
dse = dyaddown(s,0)
dse =
2 4 6 8 10
dso = dyaddown(s,1) % Downsample elements with odd indices.
dso =
1 3 5 7 9
% For a matrix.
s = (1:3)'*(1:4)
s =
1 2 3 4
2 4 6 8
3 6 9 12
dec = dyaddown(s,0,'c') % Downsample columns with even indices.
dec =
2 4
4 8
6 12
der = dyaddown(s,1,'r') % Downsample rows with odd indices.
der =
1 2 3 4
3 6 9 12
dem = dyaddown(s,1,'m') % Downsample rows and columns
% with odd indices.
dem =
1 3
3 9
Strang, G.; T. Nguyen (1996), Wavelets and Filter Banks, Wellesley-Cambridge Press.