persistent tsqrt2 x1 ;
if isempty(tsqrt2), tsqrt2=0; end;
if isempty(x1), x1=0; end;
%***BEGIN PROLOGUE COSQB
%***PURPOSE Compute the unnormalized inverse cosine transform.
%***LIBRARY SLATEC (FFTPACK)
%***TYPE SINGLE PRECISION (COSQB-S)
%***KEYWORDS FFTPACK, INVERSE COSINE FOURIER TRANSFORM
%***AUTHOR Swarztrauber, P. N., (NCAR)
% subroutine COSQB computes the fast Fourier transform of quarter
% wave data. That is, COSQB computes a sequence from its
% representation in terms of a cosine series with odd wave numbers.
% The transform is defined below at output parameter X.
% COSQB is the unnormalized inverse of COSQF since a call of COSQB
% followed by a call of COSQF will multiply the input sequence X
% by 4*N.
% The array WSAVE which is used by subroutine COSQB must be
% initialized by calling subroutine COSQI(N,WSAVE).
% Input Parameters
% N the length of the array X to be transformed. The method
% is most efficient when N is a product of small primes.
% X an array which contains the sequence to be transformed
% WSAVE a work array which must be dimensioned at least 3*N+15
% in the program that calls COSQB. The WSAVE array must be
% initialized by calling subroutine COSQI(N,WSAVE), and a
% different WSAVE array must be used for each different
% value of N. This initialization does not have to be
% repeated so long as N remains unchanged. Thus subsequent
% transforms can be obtained faster than the first.
% Output Parameters
% X For I=1,...,N
% X(I)= the sum from K=1 to K=N of
% A call of COSQB followed by a call of
% COSQF will multiply the sequence X by 4*N.
% Therefore COSQF is the unnormalized inverse
% of COSQB.
% WSAVE contains initialization calculations which must not
% be destroyed between calls of COSQB or COSQF.
%***REFERENCES P. N. Swarztrauber, Vectorizing the FFTs, in Parallel
% Computations (G. Rodrigue, ed.), Academic Press,
% 1982, pp. 51-83.
%***ROUTINES CALLED COSQB1
%***REVISION HISTORY (YYMMDD)
% 790601 DATE WRITTEN
% 830401 Modified to use SLATEC library source file format.
% 860115 Modified by Ron Boisvert to adhere to Fortran 77 by
% (a) changing dummy array size declarations (1) to (*),
% (b) changing definition of variable TSQRT2 by using
% FORTRAN intrinsic function SQRT instead of a DATA
% 861211 REVISION DATE from Version 3.2
% 881128 Modified by Dick Valent to meet prologue standards.
% 891214 Prologue converted to Version 4.0 format. (BAB)
% 920501 Reformatted the REFERENCES section. (WRB)
%***end PROLOGUE COSQB
%***FIRST EXECUTABLE STATEMENT COSQB
tsqrt2 = 2..*sqrt(2.);
if( n<2 )
x(1) = 4..*x(1);
elseif( n==2 ) ;
x1 = 4..*(x(1)+x(2));
x(2) = tsqrt2.*(x(1)-x(2));
x(1) = x1;
[n,x,wsave,dumvar4]=cosqb1(n,x,wsave,wsave(sub2ind(size(wsave),max(n+1,1)):end)); dumvar4i=find((wsave(sub2ind(size(wsave),max(n+1,1)):end))~=(dumvar4)); wsave(n+1-1+dumvar4i)=dumvar4(dumvar4i);