Provides a variety of apodization windows.

w = apowin(Type,nPoints)
w = apowin(Type,nPoints,alpha)

apowin returns an apodization window with nPoints point in the column vector w. WindowType is a string specifying the window type. The available types are listed in the following table.

Type	Name	Function over
bar	Bartlett
wel	Welch
con	Connes
cos	Cosine
han	Hann
ham	Hamming
bla	Blackman
exp	Exponential
gau	Gaussian
kai	Kaiser

The returned window is symmetric. If a '+' is appended to the three-letter type string, only the right part of the symmetric window function () is returned. If a '-' is appended, the left part () is returned. E.g., 'exp+' thus specifies an exponential decay.

alpha is a parameter which is required for the Kaiser, Gaussian and exponential windows. Reasonable ranges for alpha are listed below.

Type	alpha range
'exp'
'gau'
'kai'

The following code plots the Kaiser windows for a range of alpha values.

y = []; n = 100;
for alpha = 3:9, y(:,end+1) = apowin('kai',n,alpha); end
plot(y);

The comparison between the Blackman, Cosine and Hann windows

n = 100; x = linspace(0,1,n);
wBla = apowin('bla+',n); wCos = apowin('cos+',n);
wHan = apowin('han+',n);
plot(x,wBla,x,wCos,x,wHan);
legend({'Blackman','Cosine','Hann'})

illustrates the difference in their behaviour at the right border.

basecorr, smooth