Failure in automating the cftool / a fourier series programmatically

I'm attempting to automate the process of fitting a fourier series to multiple x,y data by using the curve fitting tool functions. Because cftool requires the use of a column vector with one column, I have preallocated the x and y data and transposed them into column format. If the deadflag~=0, I want the code to skip the curve fitting and re-enter the loop.

Basically, I want seperate curve fits (i.e., indepedent functions, a, b, w parameter values and R^2 values) for 'k' number of columns of x and y. When I run the code, I don't get any errors, but the respective curve fitting data isn't created. Sorry in advance for my terrible coding- I'm a self-taught programming newbie. :/ Here's what I have so far:

%Preallocate x and y data
x_k=zeros(numcells,numdatapoints);
x_yes=1:numdatapoints;
x_no=zeros(1,numdatapoints);
for k=1:numcells-1
  if deadflag(k)==0
  x_k(k,:)=x_yes;
  else
  x_k(k,:)=x_no;  
  end
end
y_k=zeros(numcells,numdatapoints);
y_k(:,:)=ydata(:,:);
%Transpose x and y data into column vectors and rename
x_cv=x_k';
y_cv=y_k';
x=x_cv(:,k);
y=y_cv(:,k);
%Curve fitting loop
f8=fittype('fourier8');
f8fit=zeros(numdatapoints);
for k=1:numcells-1
  if deadflag(k)==0
  f8fit(k)=fit([x,y],f8);
  else
  break;
  end
end