'find' returning empty vector

I've written this section of code:

for k=0.05:0.05:38

index=find(A(:,2)==k);

c=max(A(index,1));

end

but for k=37.7, it returns index as a 0x1 empty double column vector. For all other values of k it works. However, when I simply do:

index=find(A(:,2)==37.7);

it returns a number. Any ideas why the loop won't? Thanks

[Stephen23]

"Any ideas why the loop won't?"

https://www.mathworks.com/help/matlab/matlab_prog/floating-point-numbers.html#f2-98690

For more discussions on this topic:

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]

tol = 10^-3 ; 
index=find(abs(A(:,2)-37.7)<tol);

Read about comparing floating point numbers.