MATLAB: How to temporarily stop a script, extract data, and then continue

debuggingfor loopif statementiterationpause

How can I temporarily pause a for loop, extract data at that point, and then continue the script? Here is my code:
A = importdata('HW8.2.Custom1.txt','%f%f%f', ' ',1);
n=length(A);  
      for i = 1:2:n-1
          line_desc = A{i};
          line_data = str2num(A{i+1});
          if strcmp(line_desc,'inlet');
              P_in = line_data(1);
              z_in = line_data(2);
              D_in = line_data(3);
          elseif strcmp(line_desc,'exit');
              P_out = line_data(1);
              z_out = line_data(2);
              D_out = line_data(3);
          elseif strcmp(line_desc,'fitting');
              K_L = line_data(1);
              V = line_data(2);
              Element_Num = line_data(3);
          elseif strcmp(line_desc,'pipe');
              L = line_data(1);
              D = line_data(2);
              rough = line_data(3);
              delta_z = line_data(4);
              Element_Num = line_data(5);
          elseif strcmp(line_desc,'pump');
              H_s = line_data(1);
              Element_Num = line_data(2);
          else strcmp(line_desc,'turbine');
              H_s = line_data(1);
              Element_Num = line_data(2);
          end
      end
What I am trying to do is stop the for loop each i, make variables based on that i, and then continue the loop and repeat for each iteration. Right now, however, it is just running the whole for loop and then giving me variables based on the final iteration (when i = n-1) Is it possible to pause it after each iteration and what function would I use?

Best Answer

What about storing the values in vectors? Then there is no need to stop the loop:
n = length(A);
P_in = zeros(1, n);  % Pre-allocate
z_in = zeros(1, n);
D_in = zeros(1, n);
inlet_i = 0;
for i = 1:2:n-1
  line_desc = A{i};
  line_data = str2num(A{i+1}); 
    switch line_desc
    case 'inlet'
      inlet_i       = inlet_i + 1;
      P_in(inlet_i) = line_data(1);
      z_in(inlet_i) = line_data(2);
      D_in(inlet_i) = line_data(3);
    case ...  same for the other variables
  end
P_in = P_in(1:inlet_i);  % Crop unused elements
z_in = z_in(1:inlet_i);
D_in = D_in(1:inlet_i);
Stopping scripts to manipulate the data is "meta-programming" and in consequence prone to errors and hard to debug.
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