'Not equal too' statement not working

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Jonathan Riley
Jonathan Riley 2015-12-1
编辑： James Tursa 2015-12-2
I have a program that gives the user a 5x5 grid and asks them to click on the stated coordinate. If they respond correctly, a second coordinate is generated. If not, an error message is displayed. A correct response is tested using the following code:
if UserResponse ~= RequiredCoordinate
Error.String = 'INCORRECT';
else
Error.String = '';
end
The problem is that it doesn't always work.
By not suppressing the variables I can see that the values aren't equal, however the code behaves as if they are equal, treating it like a correct response. But this problem only occurs sometimes.
I've run the code on 3 different machines, all running the same version (R2015, 1 machine runs a student license if that makes a difference) and sometimes the code runs as expected and others this problem occurs.
Can anyone suggest a solution?
Thank you.
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Jonathan Riley
Jonathan Riley 2015-12-1
Both variables are of type 1x2 double - e.g. [5,3]
dpb
dpb 2015-12-1
Try
~all(UserResponse==RequiredCoordinate)
instead or if the values aren't integers see the FAQ (and will still need the above if is an array of coordinates rather than single value)--
Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero

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回答（2 个）

dpb
dpb 2015-12-2
As noted in the above comment prior to seeing your response...
>> x=[5,3]; y=[5,2];
>> all(x==y)
ans =
0
>> y(2)=3;
>> all(x==y)
ans =
1
>>
Again, note the caution re: floating point comparisons if the values aren't integer; you'll have to use "fuzzy" comparison for a robust test.
James Tursa
James Tursa 2015-12-2
编辑：James Tursa 2015-12-2
Another method using the function isequal, which is useful for arrays:
if ~isequal(UserResponse,RequiredCoordinate)

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