plot error variables not same length

I'm highly suspicious that the error has to do with line 26, "f = fs*(0:Nsamps/2-1)/Nsamps; " The error I get when I run the program below is:

"Error using plot Vectors must be the same length. Error in CleanAdaptFiltered (line 31) plot(f, y_fft);"

f is a row 1x2000 Nsamps size? I'm not sure of. Something to with the lengthe of t? t is row 1x4001. I've changed too Nsamps = length(ich) and changing line 26 too, "f = fs(1/(dt*Nsamps)*(0:Nsamps));" and "f = 1/(dt*Nsamps)*(0:Nsamps);", same problem.

load AdaptiveFilteredData
d = AdaptiveFilteredData;
fs =100;
dt = .001;
t = 0:dt:4.0001;

%ich = AdaptiveFilteredData.ichannel;
%qch = AdaptiveFilteredData.qchannel;

%plot(ich,qch);



%%PLOTS
%plot(t,ich);
%plot(t,qch);


figure;
plot(t,ich)
xlabel('time(s)');
ylabel('Amplitude');
grid on
Nsamps = length(t);                  % Window length
y_fft = abs(fft(ich));                 %Retain Magnitude
f = fs*(0:Nsamps/2-1)/Nsamps;           %Prepare freq data for plot

figure;
plot(f, y_fft);                         % FFT plot
xlim([0 1]);
xlabel('Frequency(Hz)');
ylabel('FFT Magnitude'); 
grid on

[Mario Malic]

Why do you divide by 2 in this line? If you want to plot(x,y), both of them have to have the same number of columns.

f = fs*(0:Nsamps/2-1)/Nsamps;  

[hosein Javan]

because the task is to plot a single-sided fourier transform spectrum. see matlab examples of how to use fft.

Answer 1

[hosein Javan]

try this if could resolve the problem. I have selected those elemnts of "y_fft" corresponding to "f" vector.

plot(f, y_fft(1:length(f)));                         % FFT plot

[Alia Hicks]

Thank you! I did as you suggested and I no longer get an error but the plot of Magnitude vs Freq is blank. Do you think this is because of how y_fft is stored as a single row of entries Nan? I don't know why it is like this it shouldn't be.

[hosein Javan]

don't mention it. y_fft is all nans? then we've got another problem calculating y_fft. yes if it is all nans no wonder the plot is empty.

what about plot(t,ich)?