How to subtract two close numbers?
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kamiR fardi
el 16 de Oct. de 2019
Comentada: kamiR fardi
el 16 de Oct. de 2019
Hi!
I've compiled the code below and i don't know why it doesn't give exact zero.
I'll appreciate if someone helps me.
format long
x=5.4;
y=x-5;
z=y-0.4;
disp(z)
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Respuesta aceptada
Stephen23
el 16 de Oct. de 2019
Editada: Stephen23
el 16 de Oct. de 2019
"..i don't know why it doesn't give exact zero."
The decimal values 5.4 and 0.4 cannot be represented exactly using binary floating point numbers, in just the same way that you cannot write 1/3 using a finite decimal fraction.
Use num2strexact see the precise decimal values of the closest floating point binary numbers:
The behaviors of floating point numbers are quite well documented, you need to learn how to write your code taking them into account. Start by reading these:
etc.etc.
This is worth reading as well:
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