求 matlab 中bode源代码

       function [magout,主引导程序源码phase,w] = bode(a,b,c,d,iu,w)

       %BODE Bode frequency response of LTI models.

       %

       % BODE(SYS) draws the Bode plot of the LTI model SYS (created with

       % either TF, ZPK, SS, or FRD). The frequency range and number of

       % points are chosen automatically.

       %

       % BODE(SYS,{ WMIN,WMAX}) draws the Bode plot for frequencies

       % between WMIN and WMAX (in radians/second).

       %

       % BODE(SYS,W) uses the user-supplied vector W of frequencies, in

       % radian/second, at which the Bode response is to be evaluated.

       % See LOGSPACE to generate logarithmically spaced frequency vectors.

       %

       % BODE(SYS1,SYS2,...,W) graphs the Bode response of multiple LTI

       % models SYS1,SYS2,... on a single plot. The frequency vector W

       % is optional. You can specify a color, line style, and marker

       % for each model, as in

       % bode(sys1,'r',sys2,'y--',sys3,'gx').

       %

       % [MAG,PHASE] = BODE(SYS,W) and [MAG,PHASE,W] = BODE(SYS) return the

       % response magnitudes and phases in degrees (along with the frequency

       % vector W if unspecified). No plot is drawn on the screen.

       % If SYS has NY outputs and NU inputs, MAG and PHASE are arrays of

       % size [NY NU LENGTH(W)] where MAG(:,:,k) and PHASE(:,:,k) determine

       % the response at the frequency W(k). To get the magnitudes in dB,

       % type MAGDB = *log(MAG).

       %

       % For discrete-time models with sample time Ts, BODE uses the

       % transformation Z = exp(j*W*Ts) to map the unit circle to the

       % real frequency axis. The frequency response is only plotted

       % for frequencies smaller than the Nyquist frequency pi/Ts, and

       % the default value 1 (second) is assumed when Ts is unspecified.

       %

       % See also BODEMAG, NICHOLS, NYQUIST, SIGMA, FREQRESP, LTIVIEW, LTIMODELS.

       % Old help

       %warning(['This calling syntax for ' mfilename ' will not be supported in the future.'])

       %BODE Bode frequency response for continuous-time linear systems.

       % BODE(A,B,C,D,IU) produces a Bode plot from the single input IU to

       % all the outputs of the continuous state-space system (A,B,C,D).

       % IU is an index into the inputs of the system and specifies which

       % input to use for the Bode response. The frequency range and

       % number of points are chosen automatically.

       %

       % BODE(NUM,DEN) produces the Bode plot for the polynomial transfer

       % function G(s) = NUM(s)/DEN(s) where NUM and DEN contain the

       % polynomial coefficients in descending powers of s.

       %

       % BODE(A,B,C,D,IU,W) or BODE(NUM,DEN,W) uses the user-supplied

       % frequency vector W which must contain the frequencies, in

       % radians/sec, at which the Bode response is to be evaluated. See

       % LOGSPACE to generate logarithmically spaced frequency vectors.

       % When invoked with left hand arguments,

       % [MAG,PHASE,W] = BODE(A,B,C,D,...)

       % [MAG,PHASE,W] = BODE(NUM,DEN,...)

       % returns the frequency vector W and matrices MAG and PHASE (in

       % degrees) with as many columns as outputs and length(W) rows. No

       % plot is drawn on the screen.

       %

       % See also LOGSPACE, SEMILOGX, MARGIN, NICHOLS, and NYQUIST.

       % J.N. Little --

       % Revised A.C.W.Grace 8--, 2-4-, 6--

       % Revised Clay M. Thompson 7-9-

       % Revised A.Potvin -1-

       % Copyright - The MathWorks, Inc.

       % $Revision: 1.1.8.2 $ $Date: // :: $

       ni = nargin;

       no = nargout;

       % Check for demo and quick exit

       if ni==0,

        eval('exresp(''bode'')')

        return

       end

       error(nargchk(2,6,ni));

       % Determine which syntax is being used

       switch ni

       case 2

        if size(a,1)>1,

        % SIMO syntax

        a = num2cell(a,2);

        den = b;

        b = cell(size(a,1),1);

        b(:) = { den};

        end

        sys = tf(a,b);

        w = [];

       case 3

        % Transfer function form with time vector

        if size(a,1)>1,

        % SIMO syntax

        a = num2cell(a,2);

        den = b;

        b = cell(size(a,1),1);

        b(:) = { den};

        end

        sys = tf(a,b);

        w = c;

       case 4

        % State space system without iu or time vector

        sys = ss(a,b,c,d);

        w = [];

       otherwise

        % State space system, with iu but w/o time vector

        if min(size(iu))>1,

        error('IU must be a vector.');

        elseif isempty(iu),

        iu = 1:size(d,2);

        end

        sys = ss(a,b(:,iu),c,d(:,iu));

        if ni<6,

        w = [];

        end

       end

       if no==0,

        bode(sys,w)

       else

        [magout,phase,w] = bode(sys,w);

        [Ny,Nu,lw] = size(magout);

        magout = reshape(magout,[Ny*Nu lw]).';

        phase = reshape(phase,[Ny*Nu lw]).';

       end

       % end bode