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function [num, den] = rcosine(Fd, Fs, type_flag, R, Delay, tol) 
%RCOSINE Design raised cosine filter. 
%   NUM = RCOSINE(Fd, Fs) designs an FIR raised cosine filter to filter a 
%   digital signal with the digital transfer sampling frequency Fd. The 
%   filter sampling frequency is Fs. Fs/Fd must be a positive integer. 
%	The default rolloff factor is 0.5, and the default filter delay 
%	is 3/Fd seconds. 
% 
%   [NUM, DEN] = RCOSINE(Fd, Fs, TYPE_FLAG) gives specific filter design 
%   instructions. TYPE_FLAG can be 'iir', 'sqrt', or a combination 
%   such as 'iir/sqrt'. The order of the arguments is not important. 
%     'fir'    Design FIR raised cosine filter (default). 
%     'iir'    Design an IIR approximation to the FIR raised cosine filter. 
%     'normal' Design the regular raised cosine filter (default). 
%     'sqrt'   Design square root raised cosine filter. 
%     'default' Use the default (FIR, Normal raised cosine filter). 
% 
%   [NUM, DEN] = RCOSINE(Fd, Fs, TYPE_FLAG, R) specifies the 
%   rolloff factor in R, which is a real number in the range [0, 1]. 
% 
%   [NUM, DEN] = RCOSINE(Fd, Fs, TYPE_FLAG, R, DELAY) specifies the filter 
%	delay in DELAY, which must be a positive integer. DELAY/Fd is the 
%	filter delay in seconds. 
% 
%   [NUM, DEN] = RCOSINE(Fd, Fs, TYPE_FLAG, R, DELAY, TOL) specifies the 
%   tolerance in TOL for IIR filter design. The default value is 0.01. 
% 
%   When the designed filter is an FIR filter, the output in DEN is 1. 
% 
%   See also RCOSFLT, RCOSIIR, RCOSFIR, RCOSDEMO. 
 
%   Copyright 1996-2001 The MathWorks, Inc. 
%   $Revision: 1.14 $ 
 
%assigned default value 
if nargin < 6 
    tol = .01; 
end; 
 
%default delay 
if nargin < 5 
    Delay = 3; 
elseif Delay <= 0 
    error('DELAY must be a positive integer in RCOSINE.') 
elseif ceil(Delay) ~= Delay 
    error('DELAY in RCOSINE must be an integer.') 
end; 
 
%default rolloff factor 
if nargin < 4 
    R = .5; 
elseif (R < 0) | (R > 1) | ~isreal(R) 
    error('The Rolloff factor, R, in RCOSINE must be a real number in the range, [0, 1].') 
end; 
 
%default type_flag 
if nargin < 3 
    type_flag = 'default'; 
elseif ~isstr(type_flag) & ~isempty(type_flag) 
    error('TYPE_FLAG in RCOSINE must be a string.'); 
end; 
 
%not enough input varible. 
if nargin < 2 
    error('Not enough input variables for RCOSINE.') 
end; 
 
type_flag = lower(type_flag); 
 
%filter type. 
if findstr(type_flag, 'sqrt') 
    filt_type = 'sqrt'; 
else 
    filt_type = 'normal'; 
end; 
 
% check the oversampling rate 
FsDFd = Fs/Fd; 
if (ceil(FsDFd) ~= FsDFd) | (FsDFd <= 1) | ~isreal(FsDFd) 
    error('Fs/Fd in RCOSINE must be an integer greater than 1.') 
end; 
 
%design the filter. 
if findstr(type_flag, 'iir') 
    [num, den] = rcosiir(R, Delay, FsDFd, 1/Fd, tol, filt_type); 
else 
    num = rcosfir(R, Delay, FsDFd, 1/Fd, filt_type); 
    den = 1; 
end; 
%end of RCOSINE.