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Help using old version of Matlab Student

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phillip
phillip 2012-8-30
回答： Manoj Kumar 2019-5-9
Hi, I periodically use an old version 5 student edition. I'm having a rather small err large problem.
This is what happens
a=[.95 .03 .05 .97]
a =
0.9500 0.0300
0.0500 0.9700
b=a-eye(2)
b =
-0.0500 0.0300
0.0500 -0.0300
det(b)
ans =
2.7756e-018
clear
b=[-.05 .03 .05 -.03]
b =
-0.0500 0.0300
0.0500 -0.0300
det(b) ans =
0
What's happening here? Thanks.

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采纳的回答

Daniel Shub
Daniel Shub 2012-8-30
This is FAQ 6.1 wrapped up in a different way. FAQ 6.1 considers
>> 0.3 - 0.2 - 0.1
ans =
-2.7756e-17
The answer is the limited precision of floats. Using the same approach outlined in the FAQ gives:
>> sprintf('%20.18f\n', [.95 .03; .05 .97]-eye(2))
ans =
-0.050000000000000044
0.050000000000000003
0.029999999999999999
-0.030000000000000027
>> sprintf('%20.18f\n', [-.05 .03 .05 -.03])
ans =
-0.050000000000000003
0.029999999999999999
0.050000000000000003
-0.029999999999999999

更多回答（1 个）

Manoj Kumar
Manoj Kumar 2019-5-9
What's wrong ?
det(b) = 0 is equivalent to det(b) = 2.7756 x 10^*(-18) =0.

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