Is it a bug?

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Haixiao Xian
Haixiao Xian on 9 Feb 2020
Commented: Star Strider on 9 Feb 2020
I found a weird situation with the number "1.4"
v=0:0.01:5;
vd=1.4;
a=0;
for i=1:length(v)
if v(i)==vd
a=1
end
end
This code doesn't make the value of "a" become "1." However, if I change the value of "vd" to any other numbers (eg. vd=1.5), this code works well. Also, if I change the range of "v" to "v=0:0.01:2", it works as well. I don't know what's wrong with my orignal codes. Can anyone help me? Thank you very much!

Accepted Answer

Star Strider
Star Strider on 9 Feb 2020
You have encountered ‘floating-point approximation error’.
See Floating-Point Numbers for an extended discussion.
Also see colon for an explanation of how it calculates the numbers in your ‘v’ vector.

More Answers (1)

Image Analyst
Image Analyst on 9 Feb 2020
Yes, you do have a bug in your program.
bugs.gif
You compared floating point numbers with == instead of ismembertol().
See the FAQ for fixes.

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