How do I save my data from each loop iteration into a single matrix?

I am trying to save each calculated variables from each run of the loop into an output file.

I have the following code, however it overwrites the data for each loop so I am only left with the final iteration's data in the end.

for i=[1:no_lines]
    x= -image_width/2 + (i-1)*d_x;
    xdc_center_focus (emit_aperture, [x 0 0]);
    xdc_focus (emit_aperture, 0, [x 0 z_focus]);
    xdc_center_focus (receive_aperture, [x 0 0]);
    xdc_focus (receive_aperture, focus_times, [x*ones(Nf,1), zeros(Nf,1), focal_zones]);
    N_pre  = round(x/(width+kerf) + N_elements/2 - N_active/2);
    N_post = N_elements - N_pre - N_active;
    apo_vector=[zeros(1,N_pre) apo zeros(1,N_post)];
    xdc_apodization (emit_aperture, 0, apo_vector);
    xdc_apodization (receive_aperture, 0, apo_vector);
    
    [rf_data, tstart]=calc_scat(emit_aperture, receive_aperture, phantom_positions, phantom_amplitudes); %output to save
    
    save(sprintf('rft%04d.mat',k),'rf_data','tstart')
    
    x = x + d_x; %adds to the x for the next iteration
end

Answer 1

[Shubham Gupta]

save(sprintf('rft%04d.mat',k),'rf_data','tstart')

There should be " i " in place "k" in the above line and you will be able to save 'rf_data' and 't_start' as rtf0001, rtf0002 and so on. I hope this answers your question

[devon foggio]

Thank you! This changed worked and allows for saving of each data set after each iteration- however is there a way to save and add into one total matrix output from the loop?

Answer 2

[Star Strider]

Without knowing what size your variables ‘rf_data’ and ‘tstart’ are, the easiest way would be to save them to cell arrays, then (if necessary) convert the cell arrays to numeric arrays after the loop, and save them then:

    [rf_data{i}, tstart{i}]=calc_scat(emit_aperture, ... 
    . . .
end
save(sprintf('rft%04d.mat',i),'rf_data','tstart')

This will create the file name using the last value of ‘i’. Change (or delete) the sprintf call if you want to save it with one specific file name.