how to define a while statement that when the variable equals a numerical value, ends the code?

Hi,

I want to write a while condition that when variable A gets a numerical value inside the loop, ends the code, otherwise continues to the code...

How can I write this while condition?

Thansks in advance,

Regards...

Answer 1

[Walter Roberson]

while ~exist('A', 'var') && ~isnumeric(A)
   ...
end

This will continue to loop until A is assigned a value and the value is numeric.

The common kinds of values that are not numeric include logical values, character strings, structures, cell arrays, function handles, graphics objects (R2014b or later), and various other kinds of objects.

[bilgesu ak]

But how should I define A before while? I write A=[]; and run the code but it doesn't enter inside the while loop and gives A =[] at the end of the code.

[Walter Roberson]

while ~exist('A', 'var') || ~isnumeric(A) || isempty(A)
 ...
end

You would not need to initialize A at all

[] is type double and so is considered a numeric value. However I have added that as a condition.

[bilgesu ak]

Thanks Roberson, now it is running true...

Answer 2

[Titus Edelhofer]

Hi,

I understand the "get's value" is meant as "being not empty" ...?

A = [];
while isempty(A)
   % do something, e.g.
   A = 42;
end

Titus

[Titus Edelhofer]

Or, if you want to run while it's not a specified value:

A = 10;
while A~=1
   % do something, e.g.
   A = A - 1;
end

Titus

[Walter Roberson]

And be careful, if your "specified value" is not an integer then it might be difficult to match it exactly due to floating point precision issues.