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vector equals to value in matrix

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Nkenna Amadi
Nkenna Amadi 2018-7-9
评论： M 2018-7-9
i have a vector, A=0.9997 and a matrix gg=(0.35:0.0001:2); when i try to run,= any(eq(A,gg)) or any(A==gg); to find if A is in gg it always returns it as zero even though it return one as it is part of the elements of gg .if i run any(eq(0.9997,gg)), it returns it as one. Is there any reason for this and how can i rectify this?

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回答（2 个）

M
M 2018-7-9
The three following expressions:
any(eq(A,gg))
any(A==gg)
any(eq(0.9997,gg))
are the same and equal to 1. What is your problem exactly?
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Nkenna Amadi
Nkenna Amadi 2018-7-9
thats my problem because i have a the value of A changes as it is a loop, so i cant just put a number
M
M 2018-7-9
You didn't say that the value of A changes in a loop. Look at Dennis' answer for more details.

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Dennis
Dennis 2018-7-9
编辑：Dennis 2018-7-9
A=0.9997 and changing A in a loop are 2 different things.
This code will return 1.
gg=(0.35:0.0001:2);
A=0.9997;
any(A==gg)
This code wont, though A is 0.9997.
gg=(0.35:0.0001:2);
A=1.0997-0.1
any(A==gg)
The reason for this is that floating point numbers are not represented 100% accurate in binary form.
You can use abs(a-b)<tolerance to avoid this.
gg=(0.35:0.0001:2);
A=1.0997-0.1
any(abs((A-gg))<1e-10)
For more information on the topic please have a look here

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