Band elimination filter init

Band Elimination Chebyshev/plot_transfer_function.m

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+function plot_transfer_function( tf, frequency_markers )
+%PLOT_TRANSFER_FUNCTION Plots bode of a transfer function with markers
+%
+%   tf                - The transfer function (created using tf)
+%   frequency_markers - A matrix of frequencies in Hz
+%
+%   Example:
+%       plot_transfer_function( tf([1000], [1 1000]), [10 1000 10000] );
+
+figure;
+x_space = logspace(1,5,1000); % 1000 points between 10^1 and 10^5
+x_space = 2 * pi * x_space; % to rad / sec
+[mag,~,wout] = bode(tf,x_space);
+mag = squeeze(mag);
+wout = squeeze(wout);
+mag = 20*log10(mag);
+wout = wout/2/pi;
+semilogx(wout,mag,'-b');
+axis([min(wout) max(wout) min(mag)-10 max(mag)+10]);
+[num,den] = tfdata(tf);
+syms s;
+d1 = digits(5);
+ltx = latex(vpa(poly2sym(cell2mat(num),s)/poly2sym(cell2mat(den),s)));
+digits(d1);
+title(strcat('$',ltx,'$'), 'Interpreter','latex', 'FontSize', 24);
+xlabel('Frequency (Hz)', 'FontSize', 18);
+ylabel('Magnitude (dB)', 'FontSize', 18);
+grid on;
+hold on;
+[dbMarks,~,frequency_markers] = bode(tf,2 * pi * frequency_markers);
+dbMarks = squeeze(dbMarks);
+frequency_markers = squeeze(frequency_markers);
+dbMarks = 20*log10(dbMarks);
+frequency_markers = frequency_markers/2/pi;
+Aw = cell(size(frequency_markers, 1) + 1, 1);
+Aw{1} = 'Transfer function';
+for i = 1 : size(frequency_markers, 1)
+    semilogx(frequency_markers(i),dbMarks(i),'o');
+    Aw{i+1} = sprintf('Attenuation at %.2f Hz is %.2f dB', ...
+        frequency_markers(i), dbMarks(i));
+end
+legend(Aw,'Location','best','FontSize',12);
+set(gca,'FontSize',14);
+end