Matlab adds a minor number to integer - why?

hi,

i noticed a very strange phenomanon:

i defined a few numbers:

t1 = 18.1

Delta = 0.1

t2 = t1 + Delta;

now open the cell of t2 and i see matlab add some very small value in the end of the decimal number, i.e.:

t2 = 18.200000000000003

what is the "3" in the end and how can i prevent it from happening?

I need the exact numbers and not additions,

tnanks,

Oded

[G A]

https://uk.mathworks.com/matlabcentral/answers/41877-matlab-floating-point-errors

Answer 1

[Stephen23]

"i noticed a very strange phenomanon:"

Nope, not strange at all.

"what is the "3" in the end..."

Accumulated floating point error.

"...and how can i prevent it from happening?"

You can't. All operations on floating point values have the potential to collect floating point error. It is simply fundemental to how those values are stored. You need to learn about the limits of floating point numbers. Start by reading these:

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