Help!! (Function definitions are not permitted in this context.)

I try to insert values into this matlab code

numer_poly = [60000];
denom_poly = [4 1];
time_delay = 0;
wrange = logspace(-3, 3, 1000);

function iok = plot_bode( numer_poly, denom_poly, time_delay, wrange);
% --- plot_bode ---
%
% iok = plot_bode( numer_poly, denom_poly, time_delay, wrange);
%
% This function plots a polar-plot for the transfer-function represented
% by the row-vectors <numer_poly> and <denom_poly> and with the time-delay
% <time_delay>. The frequency range is <wrange> (if specified).
%
% The last two arguments in the list can be omitted.
% The function is capable of choosing default values for both of these.
% ---------------------------------------------------------------------

jot = sqrt(-1);
iok = 0;

if (nargin < 3)
   time_delay = 0.0;
end

if (nargin < 4)  % --- Establish default frequency range. ---
   ruuts_numer = roots(numer_poly);
   ruuts_denom = roots(denom_poly);
   all_ruuts = [ ruuts_numer;  ruuts_denom ];
   max_ruuts = max(abs(all_ruuts));   % Find a maximum frequency. 
   max_ru = max_ruuts*1000;          
   % --- Exercise caution to ensure that time-delay does not produce
   %     crazy rotations at the end.
   if ( (time_delay*max_ru)/5000 > (0.1*pi) )
      max_ru = 5000*(0.1*pi) / time_delay;
   end

     tx = max_ruuts * 1.0E-12;      % Min freq. not to be lower than this.
     min_ruuts = min(abs(all_ruuts));   % Find a minimum frequency. 
     min_ru = min_ruuts/1000;
     min_ru = max([ min_ru,  tx ]);

     frqs = (logspace(log10(min_ru), log10(max_ru),5001))';
  else
     frqs = wrange;
  end

% --- Now assess the orders of numerator and denominator. 
order_num = max(size(numer_poly))-1;
t_num     = min(size(numer_poly));
order_dnm = max(size(denom_poly))-1;
t_dnm     = min(size(denom_poly));
s_values = jot*frqs;

% --- --- First compute the denominator. 
t_values = s_values*0.0+1;   % This will represent (s_values.^ii)
d_values = s_values*0.0;     % This will represent the summation. 
for ii=1:order_dnm+1;
   d_values = d_values + t_values*denom_poly(order_dnm+2-ii);
   t_values = t_values.*s_values;
end
% --- --- Next compute the numerator. 
t_values = s_values*0.0+1;   % This will represent (s_values.^ii)
n_values = s_values*0.0;     % This will represent the summation. 
for ii=1:order_num+1;
   n_values = n_values + t_values*numer_poly(order_num+2-ii);
   t_values = t_values.*s_values;
end
% --- --- Finally combine them. 
xfer_values = (n_values./d_values);

disp(' '); disp(' ');  td = 0.0;
% td = input(' Enter the amount of pure time-delay (s) to include : ');
phase_lags = td*frqs;

xfer_angs = unwrap(angle((xfer_values)-phase_lags));

if ( max(abs( xfer_values )) < 1)
   disp(' ');
   disp(' This transfer function has gain < 1 for all frequencies ');
   disp(' Phase Margin is not meaningful ');
   disp(' ');  pause(1);
   low_gain = 1;
elseif ( min(abs( xfer_values )) > 1)
   disp(' ');
   disp(' This transfer function has gain > 1 for all frequencies in range');
   disp(' Phase Margin is not meaningful here ');
   disp(' ');  pause(1);
   low_gain = 1;
else 
   disp(' ');
   itx = first_crss( log(abs(xfer_values)) );
   % disp([' itx = ' int2str(itx)]), pause
   frq_0dB = frqs(itx);  phs_0dB = xfer_angs(itx);
   disp([' Frequency where gain closest to unity is ' num2str(frq_0dB) ' (rad/s) ']);
   disp([' Phase at that frequency = ' num2str(phs_0dB*180/pi) ' degrees ']);
   PM = phs_0dB+pi;
   disp([' Phase margin = ' num2str(PM*180/pi) ' degrees ']);
   disp(' ');  pause(1);
   low_gain = 0;
end

if ( min( xfer_angs ) > -pi );
   disp(' ');
   disp(' This transfer function has phase > -<pi> for all frequencies ');
   disp(' Gain Margin is not meaningful ');
   disp(' ');  pause(1);
   low_lag = 1;
else
   disp(' ');
   [junk,itx] = min(abs( xfer_angs + pi) );
   frq_180d = frqs(itx);  gaindB_180d = 20*log10(abs(xfer_values(itx)));
   disp([' Freq. where phase closest to -180 degrees is ' num2str(frq_180d) ' (rad/s) ']);
   disp([' Gain at that frequency = ' num2str(gaindB_180d) ' dB ']);
   GM = 0-gaindB_180d;
   disp([' Gain margin = ' num2str(GM) ' dB ']);
   disp(' ');  pause(1);
   low_lag = 0;
end

figure(1);
subplot(211);
semilogx(frqs, 20*log10(abs(xfer_values)),'linewidth',2)';
grid on;
hold on;
semilogx(frqs, 0,'r-');
if (low_lag==0)
   semilogx([ frq_180d; frq_180d ], [0  gaindB_180d], 'k','linewidth',2);
end
axis([ min(frqs)  max(frqs)  min(log10(abs(xfer_values)))*20 max(log10(abs(xfer_values)))*20 ]);
hold off;
xlabel(' Frequency (rad/s) ');
ylabel(' Gain (dBs) ');

subplot(212);
semilogx(frqs, xfer_angs*180/pi,'linewidth',2)';
grid on;
hold on;
semilogx(frqs, (frqs*0-180),'r-');
if (low_gain==0)
   semilogx([ frq_0dB; frq_0dB ], [phs_0dB*180/pi  -180], 'k','linewidth',2);
end
axis([ min(frqs)  max(frqs)  -360  180 ]);
hold off;
xlabel(' Frequency (rad/s) ');
ylabel(' Phase angle (degrees) ');

but it keeps telling me this error

??? Error: File: plot_bode.m Line: 6 Column: 1 Function definitions are not permitted in this context.

What should I do?

Answer 1

[C.J. Harris]

What you are doing is mixing a script and a function within a single m-file. Remove the first four lines:

numer_poly = [60000];
denom_poly = [4 1];
time_delay = 0;
wrange = logspace(-3, 3, 1000);

These variables needs to be defined elsewhere, not within the same m-file as the function.

See the documentation to fully understand the difference between a script and a function.

[Sean de Wolski]

or just write function at the top line to turn the script into a function.