MATLAB: How to have variables displayed in workspace after every while loop iteration

loopsvariableswhile loopworkspace

Hi all,

I have a while loop in which my variables are only stored in the workspace after the entire loop is completed. Is there any way that I can store the variable in the workspace after each iteration of the loop, because I need to use these values while the loop is still running. Thank you!

Best Answer

The easiest way (without seeing your code) is to initialise a counter before the loop, increment it within the loop, and subscript the variables calculated in the loop:

k1 = 1;
while some_condition
    a(k1) = some_expression;
    b(k1) = some_other_expression + a(k1);
    k1 = k1+1;
end

Here, â€˜aâ€™ and â€˜bâ€™ will be available as vectors at the end of the loop, and available to each other within the loop. Thatâ€™s as specific as I can get.

Related Solutions

MATLAB: Leave the whole for-loop

Why can't you use break? The break command can perfectly be used in combination with if statements. Break will execute the innermost for (or while) loop it is in...

Consider the following example:

   for ii = 1:10
       disp(['Current value of ii = ', num2str(ii)])
       if ii>5
           % execute some for loops
           for kk=1:5
               for ll=1:5
                   % put your commands here
               end
           end
           % exit the for loop
           break 
       else
           for kk=1:5
              % do something here 
           end
       end 
   end
   disp(['for loop was stopped at the moment that ii = ', num2str(ii)])

The break command will exit the innermost loop (type: help break):

break Terminate execution of WHILE or FOR loop.
    break terminates the execution of FOR and WHILE loops.
    In nested loops, break exits from the innermost loop only.

Does this clarifies it for you?

MATLAB: In an assignment A(I) = B, the number of elements in B and I must be the same? While Loop

Nancy - if nothing is in front of the sensor, then (as you say) nothing is being read. So you need to guard against the case when this happens because the failure is (probably) occurring when value is an empty string, and the str2num(value) becomes an empty matrix which you try to assign to your vector out - so the code is trying to assign zero elements to one element, and so the error makes sense.

Try the following

 out=[];
 for i=1:60
     [value,count] = fscanf(s);
     if count>0
         out(length(out) + 1) = str2num(value);
     end
     disp(out);
 end

where we use the number of values read, count, to determine if we have any data to add to out. An alternative would be the following condition

 [value,count] = fscanf(s);
 if ~isempty(value)
     out(length(out) + 1) = str2num(value);
 end

So if our value string is non-empty, then convert it to a number and add it to out. If you are only ever reading in numbers or nothing, then the above will be fine. But if for some reason your value is

 value = '123a';

then the

 str2num(value)
 ans =
     []

returns an empty matrix too which will generate an error. And so it may be safer to do

 out=[];
 for i=1:60
     [value,count] = fscanf(s);
     if count>0
         valueAsNum = str2um(value);
         if ~isempty(valueAsNum)
             out = [out ; valueAsNum];
         end
     end
     disp(out);
 end

Note the alternative for updating the out vector.

Best Answer

Related Solutions

MATLAB: Leave the whole for-loop

MATLAB: In an assignment A(I) = B, the number of elements in B and I must be the same? While Loop

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