Comparative Operator result is wrong

I tried to run the if statement but this happens.

The result must be true(=1) in the last instruction but it returns false(=0)...

Anyone knows what is the problem???

[Stephen23]

"Anyone knows what is the problem???"

The assumption that binary floating point numbers have infinite precision:

https://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

https://www.mathworks.com/matlabcentral/answers/316889-why-two-equal-numbers-are-not-equal

http://www.mathworks.com/matlabcentral/answers/102419-how-do-i-determine-if-the-error-in-my-answer-is-the-result-of-round-off-error-or-a-bug

http://www.mathworks.com/matlabcentral/answers/140656-about-numerical-difficulty-of-equality-comparison-operation-between-two-double-real-numbers-in-matlab

This is worth reading as well:

https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

http://faculty.tarleton.edu/agapie/documents/cs_343_arch/papers/1991_Goldberg_FloatingPoint.pdf

Answer 1

[KSSV]

Note that you are comparing two floating point numbers and such numbers cannot be comapred using ==. Follow

tol = 10^-5 ; 
idx = abs(val1-val2)<tol

[여춘 박]

Thanks!

Answer 2

[Steven Lord]

Two numbers that are displayed the same may not represent the same stored value. See this Answers post for more information about floating point numbers.

[여춘 박]

Thanks!

Answer 3

[Image Analyst]

See the FAQ: FAQ Why is 0.3 - 0.2 - 0.1 or similar not equal to zero?