% for_sines.m

% yourname and lab section
    fprintf('\n Gretchen Paden, Th 3:00-5:00 \n');
% initialize t and sine to zeros
    t=zeros(1,251);
    sine=zeros(3,length(t));

%    sin_t(1,:) = sin(2*pi*f(1).*t)
%        t = 0:.01:2.5
%        f = 6:2:10

%you don't need any of these lines, and you're supposed to initialize t, f using a for loop.
%(your method is actually better, but that's not what's assigned).

% initialize f to its proper values using a "for" loop

    for f=0:.01:2.5
    disp(f)
    end
%all you're doing here is displaying numbers.  you need to store (6,8,10) into an array, f.

% initialize t to its proper values using a "for" loop
    for t = 0:.01:2.5
    disp(f)
    end

%same as above, but now you want to store the values into an array, t.

% calculate the sine and plot using a "for" loop

%you should do this in 2 steps.  first calculate the sin values, and then plot.
%you'll need to loop over f and t.

    figure;
    for ii


      y(ii,;)=sin(2*pi*f(ii).*t);
      subplot(3,1,ii)
      plot(x,y(1,:),'k');
      ylabel('y');
      xlabel('x');
      title('Frequency');
      grid on
    end