Surface plot using multiple excel files - matlab

Question

I'm just a beginner with MATLAB.
I need to represent my data using a 3D plot. I tried using the surf function but in my case this is a little bit tricky. From the code you will see that I am looping through multiple excel files to extract data from it.
Using a 3-dimensional plot I need to represent my Fv array as the 'X' coordinate, my FTsiga as the 'Y' coordinate and the the third coordinate should be each excel file that I am looping through.
A plot of (Fv,FTsiga) looks like the figure that is attached herewith.
Fv(x-axis) , FTsiga(y-axis)
The code that I have written so far couldn't seem to execute because MATLAB crashed due to insufficient memory or because it got stuck in a loop. The latter is more likely I guess.
% Matlab trial code: Trying to loop through excel files strored in directory
source_dir = 'C:\UTwente\Q4\Structural Health and Condition monitoring\Case Roadbridge (Zwartewaterbrug)\Excel data'
source_files = dir(fullfile(source_dir, '*xlsx'));
len = length(source_files);
matrix = zeros(len,32);
X = zeros(len,32); Y = zeros(len,32); Z = zeros(len,32);
%looping through excel file in directory
for i=1:len
data= xlsread(source_files(i).name,'Measurement data');
for j=1:32
sig = data(:,j);
sig = sig - mean(sig); % Remove d-c Offset
L = length(sig);
Fs = 1000; % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
FTsig = fft(sig)/L;
Fv = linspace(0, 1, fix(length(FTsig)/2)+1)*Fn; % Frequency Vector
Iv = 1:length(Fv); % Index Vector
FTsiga = double(abs(FTsig(Iv))*2); % Truncate, Magnitude, Convert To Double
sgf_sm = sgolayfilt(FTsiga, 5, 501); % Create ‘sgolayfilt’ Filtered FFT
[~, idx] = max( sgf_sm ); % Getting the value of the modal frequency
peakfreq = Fv( idx );
matrix(i,j) = peakfreq; % Matrix of all peak frequencies
[X,Y,Z] = meshgrid(Fv,FTsiga,i);
end
surf(Fv,FTsiga,i);
end