How to get a number with significant k-digits in MatLab? - vpa -- MatLab

How to get a number with significant k-digits in MatLab?

[Ans]

vpa

[syntax]

vpa(x)

vpa(x,a)

[description]

vpa(x,a) 

It will return x with significant k-digits.

The default value of k is digitOld

where it is 32 by default.

You can also set the value digitOld through the keyword digits

more details on digits:

Change variable precision used - MATLAB digits (mathworks.com)

[NOTE]

Don't know about the meaning of significant k-digits. You can see the link in the section below which named "chinese definition".

This link gives a great definition.

more details on:

MathWork official doc

Variable-precision arithmetic (arbitrary-precision arithmetic) - MATLAB vpa (mathworks.com)

chinese definition

matlab中vpa函數 matlab有效數位 – MATLAB中文論壇 (ilovematlab.cn)

code:

clear

clc

fprintf("pi in 5 precision in a float-point number.\n")

pi

fprintf("pi in 32 precision in a float-point number.\n")

pi32 = vpa(pi)

fprintf("pi in 32 precision in a float-point number.\n")

pi32 = vpa(pi,32)

fprintf("pi in 31 precision in a float-point number.\n")

pi31=vpa(pi,31)

fprintf("pi in 3 precision in a float-point number.\n")

digitsOld=digits(3);

pi3=vpa(pi)

fprintf("current float-point precision.\n")

digitsOld

result:

pi in 5 precision in a float-point number.

ans =

3.1416

pi in 32 precision in a float-point number.

pi32 =

3.14

pi in 32 precision in a float-point number.

pi32 =

3.1415926535897932384626433832795

pi in 31 precision in a float-point number.

pi31 =

3.14159265358979323846264338328

pi in 3 precision in a float-point number.

pi3 =

3.14

current float-point precision.

digitsOld =

3