I have this code in MATLAB:
for i = 1: n
a = randi([0 500]);
function (a);
end
When there is error during the execution of function(a) in iteration i=k the program stops. Is there any way to make the program repeat the same iteration (when there is an error) with a new value of a and continue the execution?
The solution to your problem is pretty simple. Just use try, catch.
For loop that calls function
for i=1:3
a=randi([0 500]);
try
myfunction(a); %Statements that may throw an error
catch
%Code that is executed if myfunction throws error
end
disp(i) %Proves that the loop continuous if myfunction throws an error
end
Function
function b = myfunction(a)
b=a;
error('Error!!!') %Function throws error every time it gets called
end
Output without try, catch
Error using myfunction (line 3)
Error!!!
Error in For_Error (line 6)
myfunction(a); %Statements that may throw an error
Output with try, catch
1
2
3
try/catch block that is this indiscriminate is not a good idea. I highly recommend only catching specific errors, as defined by function, and rethrowing ones that do not match.
@user3288977 You do not have to write something into the catch block and depending on the application that could be totally okay. It is difficult to suggest something without knowing what your code is supposed to do. One possibility would be to create an error message to the user that explains what the cause of the exception might be (see try, catch documentation).
try/catch skips the iteration where there is an error and continue the loop... But I want to re-execute the same iteration where the error occurs... I hope the idea is clearI think Kaspar answer is not exactly answering your question, user3717023.
In Kaspar solution iteration is not repeated but simply skipped (like when using continue).
Proposed solution
If you want MATLAB to repeat iteration until myfunction() is completed successfully use while. Look at this this:
for ii = 1:30
disp(ii)
out = 0;
while(~out)
disp('Attempt ...')
try
out = myfunction(some_arguments);
catch
disp('F****ck!')
end
pause(1)
end
disp('OK !')
end
If myfunction returns its output (which will happen if there was no error) it finishes while loop.
Lines with disp added for self-descriptivity.
Line with pause added for neat output when running example.
Example
Run code above with below example of myfunction() to check how this solution works:
function out = myfunction(x)
a = randi(2,1,1) - 1; % a = 0 or a = 1
if a==0
error
else
out = magic(3);
end
end
Example output:
ii =
1
Attempt ...
F****ck!
Attempt ...
OK !
ii =
2
Attempt ...
OK !
ii =
3
Attempt ...
F****ck!
Attempt ...
F****ck!
Attempt ...
F****ck!
Attempt ...
F****ck!
Attempt ...
OK !
functionso that it doesn't produce errors.whileloop with an incrementing counter based on the success offunctionor atry/catchstatement.