How to plot LTspice graph in Matlab in this case?

Hello,

I'm trying to use matlab to plot the bode plot exported from LTspice. The .txt file as well as my code is added below. I wonder why matlab keep warning me that "plot" is not proper, but I can't fix it. I really appreciate it if anyone can tell me how to solve it. And my code is listed below.

plot (Freq1,Vvo1);

hold on

xlabel('Freq (Hz)');

ylabel('Magnitude (dB)');

grid on

Answer 1

[Star Strider]

One approach —

T1 = readtable('final_all1.txt', 'VariableNamingRule','preserve')

T1 = 261×2 table
      Freq.                             V(vo)                       
    _________    ___________________________________________________

        0.001    {'(8.14596880037347e+01dB,-1.08562817812189e-04°)'}
     0.001122    {'(8.14596880035216e+01dB,-1.21809484544416e-04°)'}
    0.0012589    {'(8.14596880032533e+01dB,-1.36672488873043e-04°)'}
    0.0014125    {'(8.14596880029152e+01dB,-1.53349053729508e-04°)'}
    0.0015849    {'(8.14596880024902e+01dB,-1.72060466847946e-04°)'}
    0.0017783    {'(8.14596880019545e+01dB,-1.93055017100971e-04°)'}
    0.0019953    {'(8.14596880012804e+01dB,-2.16611289116791e-04°)'}
    0.0022387    {'(8.14596880004315e+01dB,-2.43041859892065e-04°)'}
    0.0025119    {'(8.14596879993632e+01dB,-2.72697446447758e-04°)'}
    0.0028184    {'(8.14596879980181e+01dB,-3.05971559559613e-04°)'}
    0.0031623    {'(8.14596879963252e+01dB,-3.43305725305582e-04°)'}
    0.0035481    {'(8.14596879941933e+01dB,-3.85195343705754e-04°)'}
    0.0039811    {'(8.14596879915092e+01dB,-4.32196262177601e-04°)'}
    0.0044668    {'(8.14596879881307e+01dB,-4.84932151008020e-04°)'}
    0.0050119    {'(8.14596879838771e+01dB,-5.44102778676502e-04°)'}
    0.0056234    {'(8.14596879785223e+01dB,-6.10493296788157e-04°)'}

T1.MagdB = str2double(extractBetween(T1{:,2},'(','dB')); 
T1.PhaseDeg = str2double(extractBetween(T1{:,2},',','°'))

T1 = 261×4 table
      Freq.                             V(vo)                           MagdB     PhaseDeg  
    _________    ___________________________________________________    _____    ___________

        0.001    {'(8.14596880037347e+01dB,-1.08562817812189e-04°)'}    81.46    -0.00010856
     0.001122    {'(8.14596880035216e+01dB,-1.21809484544416e-04°)'}    81.46    -0.00012181
    0.0012589    {'(8.14596880032533e+01dB,-1.36672488873043e-04°)'}    81.46    -0.00013667
    0.0014125    {'(8.14596880029152e+01dB,-1.53349053729508e-04°)'}    81.46    -0.00015335
    0.0015849    {'(8.14596880024902e+01dB,-1.72060466847946e-04°)'}    81.46    -0.00017206
    0.0017783    {'(8.14596880019545e+01dB,-1.93055017100971e-04°)'}    81.46    -0.00019306
    0.0019953    {'(8.14596880012804e+01dB,-2.16611289116791e-04°)'}    81.46    -0.00021661
    0.0022387    {'(8.14596880004315e+01dB,-2.43041859892065e-04°)'}    81.46    -0.00024304
    0.0025119    {'(8.14596879993632e+01dB,-2.72697446447758e-04°)'}    81.46     -0.0002727
    0.0028184    {'(8.14596879980181e+01dB,-3.05971559559613e-04°)'}    81.46    -0.00030597
    0.0031623    {'(8.14596879963252e+01dB,-3.43305725305582e-04°)'}    81.46    -0.00034331
    0.0035481    {'(8.14596879941933e+01dB,-3.85195343705754e-04°)'}    81.46     -0.0003852
    0.0039811    {'(8.14596879915092e+01dB,-4.32196262177601e-04°)'}    81.46     -0.0004322
    0.0044668    {'(8.14596879881307e+01dB,-4.84932151008020e-04°)'}    81.46    -0.00048493
    0.0050119    {'(8.14596879838771e+01dB,-5.44102778676502e-04°)'}    81.46     -0.0005441
    0.0056234    {'(8.14596879785223e+01dB,-6.10493296788157e-04°)'}    81.46    -0.00061049

figure
subplot(2,1,1)
semilogx(T1.('Freq.'), T1.MagdB)
grid
ylabel('Magnitude (dB)')
subplot(2,1,2)
semilogx(T1.('Freq.'), T1.PhaseDeg)
ylabel('Phase (°)')
grid
xlabel('Frequency')
sgtitle('Bode Plot of LTSpice Data')

There may be more efficient ways to extract the data, however this works.

To unwrap the phase data:

T1.PhaseDegU = rad2deg(unwrap(deg2rad(T1.PhaseDeg)))

and plot that instead for the phase. Otherwise, just leave it as it is.

.

[Huihong]

Thanks a lot for your help!

[Star Strider]

As always, my pleasure!