MATLAB: Is double precision standard in matlab? How to calculate in that precision.

changing precisiondouble precisions

I am trying to calculate expressions in double precision arithmetic in matlab. Is that standard or do I have to change it? And how would I change to any other precision?

Best Answer

Hi,

yes double precision is standard in Matlab that represents floating-points numbers in either double-precision or single-precision format .

Matlab constructs double data type according to IEEE Standard 754 for double precision, and any value stored as double requires 8 bytes.

Related Solutions

MATLAB: Matlab integer format for answer

Try a function, like int32(), fix(), ceil(), floor(), uint8(), int32(round()), etc.

a = (2+24)/(4*3) % Floating point.
aInteger = int32(a)
whos aInteger; % int32
aInteger = round(a)
whos aInteger; % Double


aInteger = floor(a)
whos aInteger; % Double
aInteger = ceil(a)
whos aInteger; % Double
aInteger = fix(a)
whos aInteger; % double
aInteger = uint16(a)
whos aInteger; % uint16

Note that with round(), ceil(), floor(), and fix() you will end up with a double but with no fractional part. If you want an actual integer, you have to cast to an integer data type with int32(), int16(), etc.

MATLAB: Matlab floating point precision.

Never trust the least significant bits of a floating point number, at least unless you know enough about the extent that you can trust them. But in general, don't.

A double precision floating point number carries roughly 16 digits, actually 52 binary bits of precision.

What happens when you add two numbers that are of different magnitude?

X0 = 1/3
X0 =
         0.333333333333333

So X0 is 1/3. Not exactly because we cannot represent the fraction 1/3 exactly in binary. But that is not really pertinent here.

sprintf('%0.55f',X0)
ans =
    '0.3333333333333333148296162562473909929394721984863281250'

Suppose we add and subtract delta?

delta = 100000.1
delta =
                  100000.1
X1 = X0 + delta - delta
X1 =
       0.333333333328483

What happened? We added a number that was more than 1e5 times as large as X0. Stored in a double, that means we lose the bottom 5 digits of the sum. Subtracting delta off again, does not help, because we already lost that information. Once information is lost, it cannot be magically regained.

Best Answer

Related Solutions

MATLAB: Matlab integer format for answer

MATLAB: Matlab floating point precision.

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