Problem in plotting using semilogx() function

Question

PVR 2014-10-19

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/159173-problem-in-plotting-using-semilogx-function

编辑： Rick Rosson 2014-10-19

I need to plot a graph between w(frequency) and Mdb(Magnitude in db) using semilogx() function for different values of w. The output of graph is null. It shows nothing and there are no errors displayed. Where did I go wrong.

R=zeros(1,10000);
I=zeros(1,10000);
Mag=zeros(1,10000);
Z=zeros(1,10000);
Y=zeros(1,10000);
Mdb=zeros(1,10000);
for *w* = 0.1:0.01:10
R=(256-(16*w^2))/((16-(w^2))^2+(10*w)^2);
I=-160*w/((16-w^2)^2+(10*w)^2);
Mag=sqrt(R^2+I^2);
Z=atan2(I,R);
Y=Z*180/pi;
*Mdb* =20*log10(Mag); *bold*
plot(w,Mdb,'g');
semilogx(w,Mdb);
end

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Answer 1

Rick Rosson 2014-10-19

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/159173-problem-in-plotting-using-semilogx-function#answer_155709

编辑：Rick Rosson 2014-10-19

在 MATLAB Online 中打开

Vectorized code, no for-loop necessary:

   w = 0.1:0.01:10;
   R = (256-(16*w.^2))./((16-(w.^2)).^2+(10*w).^2);
   I = -160*w./((16-w.^2).^2+(10*w).^2);
   X = complex(R,I);
   Mag = abs(X);
   Mdb = 20*log10(Mag);
   phi = angle(X)*180/pi;
   figure;
   ax(1) = subplot(2,1,1);
   semilogx(w,Mdb);
   grid on;
   xlabel('Frequency');
   ylabel('Magnitude in dB');
   ax(2) = subplot(2,1,2);
   semilogx(w,phi);
   grid on;
   xlabel('Frequency');
   ylabel('Phase angle in degrees');
   linkaxes(ax,'x');