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While Loop, with a user made function

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James Wilson
James Wilson on 22 Apr 2021
Commented: David Hill on 22 Apr 2021
I am trying to create a while loop that compares the output of a function that is perviously in the script code to a loaded martix. I am trying to use a variable to account for the amount generators producing the power. Both usage matrix and the T_Energy martix are the same size.
Gen = 1;
T_Energy = Gen*Energy_Out;
while T_Energy < usage
T_Energy = Gen*Energy_Out;
Gen = Gen + 1;
end
Once the code is ran, the Gen value still stays at 1, and it doesn't look like the martices are compared.

Accepted Answer

Steven Lord
Steven Lord on 22 Apr 2021
From the documentation for the while keyword: "while expression, statements, end evaluates an expression, and repeats the execution of a group of statements in a loop while the expression is true. An expression is true when its result is nonempty and contains only nonzero elements (logical or real numeric). Otherwise, the expression is false."
So if your condition is nonempty and nonscalar, for the body of the while statement to execute all the elements of the condition must be true.
while [1 2] < 1.5
disp("Yes!")
end
Nothing gets displayed by that code. While 1 is less than 1.5, 2 is not. If you want the condition to be considered satisfied if any of the elements of the condition are true:
iter = 0;
while any([1 2] < 1.5) & iter < 5
disp("Yes!")
iter = iter + 1;
end
Yes! Yes! Yes! Yes! Yes!
I added the iter variable so this wasn't an infinite loop.

More Answers (2)

Walter Roberson
Walter Roberson on 22 Apr 2021
while TEST
is the same as
while all(reshape(TEST, [], 1))
In other words it is considered false if there is even one entry in TEST that is 0.
Your condition is true for some elements of it but false for other elements of it, and while stops at the first false.

David Hill
David Hill on 22 Apr 2021
You will need to figure out how you want to compare the maxtrices, less than (<) compares element-to-element producing a logical matrix the same size. When you apply the if statement, it only looks at the first element of the logical matrix. You could sum all elements and compare, but I don't know what you want.
if sum(T_Energy,'all')<sum(usage,'all')
  2 Comments
David Hill
David Hill on 22 Apr 2021
Thanks, I should have tested that hypotheses.

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