Floating point numeric problem

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Qian Feng
Qian Feng on 9 Dec 2016
Commented: Star Strider on 17 Dec 2016
I encounter a problem which I cannot understand.
a = 1.228269:0.000001:1.22828;
b = 1.228265:0.000001:1.22828;
>> ismember(a,b)
ans =
1×12 logical array
0 1 0 1 1 1 1 1 1 1 1 1
It is clearly to see that the logical array is not compatible with the values in vectors a and b. An expert has suggested that this has to do with the floating point numerics, do anyone can explain what happened to this example and how to we circumvent it ? Thanks a lot !

Accepted Answer

Star Strider
Star Strider on 9 Dec 2016
What happened is best explained in: Why is 0.3 - 0.2 - 0.1 (or similar) not equal to zero?
You can circumvent it using the ismembertol function (in R2015a and later versions).

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