how to perform fft in matlab using a set of data from excel sheet

Fs=3800;
Ts=1/Fs;
t=0:Ts:1;
L=97;
Y=abs(fft(VarName1)); %varname1 is the filename of the excel sheet
P1=Y/L;
P2=P1(1:(L+1)/2);
P2(2:end-1)=2*P2(2:end-1);
f=Fs*(0:(L/2))/L;
plot(f,P2)
xlabel('frequency')
ylabel('magnitude of P1')

Is this correct?

Answer 1

[Star Strider]

I doubt if your code would work.

Try mine:

[d,s] = xlsread(VarName1);                              % Data in ‘d’
Fs=3800;                                                % Sampling Frequency
Ts=1/Fs;                                                % Sampling Interval
Fn = Fs/2;                                              % Nyquist Frequency
L = size(d,1);                                          % Length Of Arrayt
t = linspace(0, 1, L);                                  % Time Vector
FTd = fft(d)/L;                                         % Complex Fourier Transform Of ‘d’
Fv = linspace(0, 1, fix(L/2)+1)*Fn;                     % Frequency Vector
Iv = 1:length(Fv);                                      % Matching Index Vector (For ‘FTd’ Addressing)

figure(1)
plot(Fv, abs(FTd(Iv))*2)
xlabel('frequency')
ylabel('magnitude of P1')

NOTE — This is UNTESTED CODE. It should work, but may require modification.

[karan hindocha]

My code works and so does yours.. could you tell me if I could do fft on the same excel sheet with two columns of data simultaneously?

[Star Strider]

‘could you tell me if I could do fft on the same excel sheet with two columns of data simultaneously?’

Yes, you can. The fft (link) function operates column-wise in a matrix, so it will take the Fourier transforms of each column with the same call to it. The frequency and index vectors will be the same as well. They should work without modification with your matrix.

[ahmad syaiful md subri]

dataset=xlsread('Group5.xlsx','Sheet1','A1:ALM1')

tstep=0.001;

N=1;

t = 0:0.001:1-0.001;

x=dataset;

X=fft(x);

n=size(x,2)/2;

spec=abs(x)/n;

freq=(0:499/2*n*tstep);

plot(freq,spec(1:500));

can somebody help me..error :

Error using plot

Vectors must be the same length.

Error in Untitled (line 11)

plot(freq,spec(1:500));