if statement inside a for loop not working

2016 10 5
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更新时间：2016 10 5
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Hi all,
Can someone please explain why this code is not working?
for a = 0.1:0.1:5
if a == 3
b = 1;
end
end
Once 'a' becomes 3, 'b' should be assigned a 1. But nothing happens.. Not sure what is going on

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Adam
Adam 2016-10-5

0 个投票

The representation of the results of floating point maths is not 100% accurate so you should never do a straight == between a number created via floating point maths and some other number. Always test within a tolerance.

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van4
van4 2016-10-5
Thank you very much. It's a bit strange to think that even though I'm incrementing by exactly 0.1, it is not in fact "exactly 0.1".
Jos (10584)
Jos (10584) 2016-10-5
Welcome to the world of computers using a limited amount of bits to represent numbers!
fprintf('%.40f\n', 0.1)

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