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### Highlights from Number to Scientific Prefix

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# Number to Scientific Prefix

### Stephen Cobeldick (view profile)

07 Oct 2011 (Updated )

Convert a numeric value to an SI prefixed string (metric/engineering). Bonus: binary prefixes!

File Information
Description

Convert a numeric scalar into a string with an SI prefix (aka metric prefix, or engineering prefix). For example the value 1000 is converted to '1 k'. A bonus function is included that converts from numeric to Binary-prefixed string, for example the value 1024 is converted to '1 Ki'.

After testing the SI-prefix submissions on MATLAB FEX (see Acknowledgements) and not finding a single one that converted all values correctly and that supported the correct SI spacing, I wrote my own functions. And then exhaustively tested them to confirm that they actually give the correct output.

These functions are particularly useful to help create publications following SI standards, or where control over significant digits and trailing zeros is required, or for including numeric values in figures.

This submission:
* Always includes the space character (required by SI rules).
* Automatically selects the most suitable prefix.
* Rounds to the requested significant figures (default==5).
* Prefix may be selected as either the full name ('kilo') or the symbol ('k').
* Trailing decimal zeros of the coefficient may be included or removed.
* Rounds up to the next prefix when significant figures require, e.g. '1 M', not '1000 k'.
* Uses simple integer even if precision is less than three (no exponent).

To convert from SI-prefixed string to numeric:
http://www.mathworks.com/matlabcentral/fileexchange/53886-scientific-prefix-to-number

### SI Prefix Examples ###

num2sip(10000)
ans = '10 k'
num2sip(10000,4,true)
ans = '10 kilo'
num2sip(10000,4,false,true)
ans = '10.00 k'

num2sip(999,2)
ans = '1 k'
num2sip(999,3)
ans = '999 '

num2sip(-5.555e9,3)
ans = '-5.56 G'

['Power: ',num2sip(200*1000^2,[],true),'watt']
ans = 'Power: 200 megawatt'

sprintf('Clock frequency is %shertz.',num2sip(1234567890,8,true))
ans = 'Clock frequency is 1.2345679 gigahertz.'

### Binary Prefix Examples ###

num2bip(10240)
ans = '10 Ki'
num2bip(10240,4,true)
ans = '10 kibi'
num2bip(10240,4,false,true)
ans = '10.00 Ki'

num2bip(1023,3)
ans = '1020 '
num2bip(1023,2)
ans = '1 Ki'

num2bip(-5.555e9,3)
ans = '-5.17 Gi'

['Memory: ',num2bip(200*1024^2,[],true),'byte']
ans = 'Memory: 200 mebibyte'

sprintf('Data saved in %sbytes.',num2bip(1234567890,8,true))
ans = 'Data saved in 1.1497809 gibibytes.'

### SI Prefixes ###

Magnitude | Symbol / Name
1000^-8 | y / yocto
1000^-7 | z / zepto
1000^-6 | a / atto
1000^-5 | f / femto
1000^-4 | p / pico
1000^-3 | n / nano
1000^-2 | u / micro
1000^-1 | m / milli
1000^0 |
1000^1 | k / kilo
1000^2 | M / mega
1000^3 | G / giga
1000^4 | T / tera
1000^5 | P / peta
1000^6 | E / exa
1000^7 | Z / zetta
1000^8 | Y / yotta

### Binary Prefixes (IEC 60027-2 A.2 and ISO/IEC 80000-13:2008) ###

Magnitude | Symbol / Name
1024^0 |
1024^1 | Ki / kibi
1024^2 | Mi / mebi
1024^3 | Gi / gibi
1024^4 | Ti / tebi
1024^5 | Pi / pebi
1024^6 | Ei / exbi
1024^7 | Zi / zebi
1024^8 | Yi / yobi

### Notes ###

These functions have been extensively tested against many edge cases, with particular attention to ensuring the correct rounding for all choices of significant figures. Compared to similar submissions available on MATLAB File Exchange, these functions correctly:
* include the space character between the coefficient and the prefix, even if there is no prefix (try 1).
* round to the requested significant figures (try 0.999 or 999e3, with 1 or 2 significant figures).
* return a coefficient without a prefix for zero and values outside the prefix range (try 0, Inf, 1E30).
* return a coefficient without an exponent when the significant digits are less than three (try 1e5 to 1 sigfig).

Acknowledgements
Required Products MATLAB
MATLAB release MATLAB 7.11 (R2010b)
MATLAB Search Path
`/`
19 May 2016 Stephen Cobeldick

### Stephen Cobeldick (view profile)

@Collin Pecora. Thank you for your feedback. The function returns 'u' because I wanted to stick to ASCII characters only, as different file formats and character encoding are not always compatible. You can easily edit the file or use |strrep| to get the result that you want.

Comment only
15 May 2016 Collin Pecora

### Collin Pecora (view profile)

Could chage micro 'u' to char(181) in your prefix cell array

15 May 2016 Collin Pecora

### Collin Pecora (view profile)

09 Nov 2011 1.1

Edit file description to be more accurate.

14 Feb 2012 1.3

Provide useage examples.

24 Aug 2012 1.5

- Allow positive/negative input value.
- Consistent handling of Inf/NaN values.

27 Aug 2012 1.6

- Fix edge case (val=1).

19 Nov 2012 1.8

Upload all four functions for converting between numeric and string, for both SI and binary.

03 Dec 2012 1.9

- Str->Num: space character between coefficient and prefix is optional.
- Str->Num: NaN and Inf may occur with prefixes.
- Help: Simplify prefix tables.

12 Feb 2013 1.10

- Edit the help section a little.

06 Jan 2014 1.11

- Add control over allowing trailing zeros in string.
- Convert all string coefficients into numeric (not just the first one).
- Return split string parts as a cell array.

10 Feb 2014 1.12

- Default is now lower-case E-notation.

14 Jul 2014 1.13

- Improve handling of trailing zeros.
- Improve input checking.

09 Nov 2015 2.0

* Split subimssion into two: one for num->str, other for str->num.
* Rename all functions.