Question

I wanted to create a vector with three values 1/6, 2/3 and 1/6. Obviously I Matlab has to convert these rational numbers into real numbers but I expected that it would maximize the precision available.

It’s storing the values as doubles but it’s storing them as –

b =

    0.1667    0.6667    0.1667

This is a huge loss of precision. Isn’t double supposed to mean 52 bits of accuracy for the fractional part of the number, why are the numbers truncated so severly?

Answer 1

The numbers are only displayed that way. Internally, they use full precision. You can use the format command to change display precision. For example:

format long

will display them as:

0.166666666666667    0.666666666666667    0.166666666666667

So the answer is simple; there is no loss of precision. It’s only a display issue.

You can read the documentation on what other formats you can use to display numbers.