The function NUM2WORDS converts a numeric scalar into a string with the number value given in English words, e.g. 1024 -> 'one thousand and twenty-four'. Optional arguments control the handling of the numeric input, as well as many string formatting and dialect options. The options are explained in this document, together with examples.
The number format is based on http://www.blackwasp.co.uk/NumberToWords.aspx
For integer values NUM2WORDS can be called without any options:
num2words(0) num2words(+1024) num2words(-1024)
ans = zero ans = one thousand and twenty-four ans = negative one thousand and twenty-four
NUM2WORDS rounds the number value to the digit specified by the order or sigfig options: sigfig rounds the input value to the requested number of significant figures, while order rounds to the specified order. The default order is zero, which means that all fractional digits are rounded to give an integer. Decimal digits can therefore be returned by selecting an appropriate value for either the order or sigfig options:
num2words(1.234) % default 'order' is zero num2words(1.234, 'order',-2) num2words(1.234, 'sigfig',3)
ans = one ans = one point two three ans = one point two three
If the trailing decimal digits are zeros, then by default they are not returned in the string. Setting the trz option to true will keep the trailing zeros up to the requested order or sigfig:
num2words(1, 'sigfig',3, 'trz',false) % default num2words(1, 'sigfig',3, 'trz',true)
ans = one ans = one point zero zero
NUM2WORDS has internal limits on the significant figures for all floating-point numbers: 15 for double, and 6 for single. These limits ensure that the least-unexpected output is returned. As NUM2WORDS is based around SPRINTF, an SPRINTF example shows why this is required:
sprintf('%#.15g',1e23) % fifteen significant figures sprintf('%#.16g',1e23) % sixteen significant figures
ans = 1.00000000000000e+023 ans = 9.999999999999999e+022
In contrast, all integer class numbers are parsed at their full precision (even UINT64, and positive and negative INT64 values):
num2words(intmax('uint64')) num2words(intmin('int64'), 'pos',true) num2words(intmax('int64'), 'pos',true)
ans = eighteen quintillion, four hundred and forty-six quadrillion, seven hundred and forty-four trillion, seventy-three billion, seven hundred and nine million, five hundred and fifty-one thousand, six hundred and fifteen ans = negative nine quintillion, two hundred and twenty-three quadrillion, three hundred and seventy-two trillion, thirty-six billion, eight hundred and fifty-four million, seven hundred and seventy-five thousand, eight hundred and eight ans = positive nine quintillion, two hundred and twenty-three quadrillion, three hundred and seventy-two trillion, thirty-six billion, eight hundred and fifty-four million, seven hundred and seventy-five thousand, eight hundred and seven
The default type: it can be used for all integer and decimal fraction values. All of the above examples use this number type.
The last number word is changed to have an ordinal ending:
num2words(1, 'type','ordinal') num2words(12, 'type','ordinal') num2words(123, 'type','ordinal')
ans = first ans = twelfth ans = one hundred and twenty-third
This uses the highest multiplier/scale (i.e. only one multiplier word) together with a significand that includes decimal digits when required. In most cases it will be useful to also specify the number of significant figures:
num2words(1234567.89, 'type','highest') num2words(1234567.89, 'type','highest', 'sigfig',2)
ans = one point two three four five six eight million ans = one point two million
Treats the number as being a value of currency, and returns a string that contains the currency unit and subunit names. The currency subunit is 1/100 of the unit, which suits almost all currencies in the world today. The currency unit and subunit names can be supplied as string arguments: the string format also selects whether the name has a regular, irregular or invariant plural form (see the NUM2WORDS help for details).
Note that the default order is changed to -2, to match the subunit.
num2words(23.5, 'type','money') num2words(23.5, 'type','money', 'unit','Pound|', 'subunit','Penny|Pence') num2words(101, 'type','money', 'unit','Dalmatian|', 'case','title') num2words(1001, 'type','money', 'unit','Night|', 'case','title')
ans = twenty-three dollars and fifty cents ans = twenty-three pounds and fifty pence ans = One Hundred and One Dalmatians ans = One Thousand and One Nights
Similar to money, but follows the style used in many countries: if no trailing subunits then the units are followed by the word 'only', and leading units are always indicated, even if they are zero (preventing fraud):
ans = five dollars only ans = zero dollars and fifty cents
The default returns a lower-case string. It is also possible to select upper-case, title-case (all words except 'and' have an initial capital letter) and sentence-case (only the first word has an initial capital):
num2words(-1023,'case','lower') % default num2words(-1023,'case','upper') num2words(-1023,'case','title') num2words(-1023,'case','sentence')
ans = negative one thousand and twenty-three ans = NEGATIVE ONE THOUSAND AND TWENTY-THREE ans = Negative One Thousand and Twenty-Three ans = Negative one thousand and twenty-three
There are some string formatting options that allow for different English dialects and style guidelines. The option defaults can be changed inside the mfile, if you wish to make another English dialect the default.
num2words(10000234,'and',true,'comma',true, 'hyphen',true) % default num2words(10000234,'and',false,'comma',false, 'hyphen',false)
ans = ten million, two hundred and thirty-four ans = ten million two hundred thirty four
NUM2WORDS always prepends 'negative' for negative number values (including negative zero). The 'positive' prefix is optional:
num2words(1, 'pos',false) % default num2words(1, 'pos',true)
ans = one ans = positive one
NUM2WORDS supports a number of common and not-so-common number scales:
- short and long scales are explained on many websites. Most contemporary English dialects use the short scale (and this is the NUM2WORDS default).
- indian number system is commonly used in South Asia (the Indian subcontinent). Defaults back to short for values greater than 1e21.
- peletier scale is used in many non-english speaking european countries.
- rowlett scale was designed to avoid the ambiguity of the short and long scales.
- knuth scale (aka -yllion) uses a logarithmic naming system to use very few names to cover a very wide range of values.
num2words(1e9, 'scale','short') % default num2words(1e9, 'scale','long') num2words(1e9, 'scale','peletier') num2words(1e9, 'scale','rowlett') num2words(1e9, 'scale','indian') num2words(1e9, 'scale','knuth')
ans = one billion ans = one thousand million ans = one milliard ans = one gillion ans = one hundred crore ans = ten myllion
The function WORDS2NUM converts a string (with a number given in English words) into a numeric value.