[TOC]

`double`

Converting an array to an array of double precision numbers

Usage

`double(A)`

A is an array of the type logical, double, complex or character.
It converts A to an array of double values.
If A is empty, it returns an empty array.
When A is not a character array, the array after conversion will have the same size as size(A).
When A is a character array, the size after conversion may be different from size(A), especially when A contains Unicode characters such as emojis.
When A is an array of complex values, it will return the same A, since complex arrays have double precision. To convert A to a real array, use real() instead.

Converting Characters To Doubles

When a character array is converted to doubles using double(), each of the characters is converted to a sequence of code units. A code unit is a 16-bit integer (UTF-16) in this app.
The number of code units varies with the character being converted. For examples,
- An ASCII character only has one code unit, which is its ASCII code.
- An emoji (such as 🚙) often has more than one code unit.
- For example, double('🚙') is a row vector of two code units, namely, [55357, 56985].
That's why double(['a';'🚙']) returns an error, since the double vectors of 'a' and '🚙' have different lengths. The former has one code unit (ASCII code 97), whereas the latter has two code units (which are 55357 and 56985).

💡 Keep this in mind. When a character array A is converted using d = double(A), the sizes size(A) and size(d) may be different. This usually happens when A contains emojis or non-ASCII characters.

Examples

Converting a character array to a double array of ASCII values.

Input

double('abc')

Output

ans =
 97.00   98.00   99.00

In this example, each of the emoji characters has multiple code units. Hence, each of the emojis is converted to a double vector of length > 1. As result, the array obtained by double() has size ([4, 21]), which is different from size(a) (equal to [4, 5]).

Input

a = ['🗻b🇦🇲✊🏾';
'💫b🇲🇶✊🏿';
'🖤f🇦🇩✊🏿';
'🏫d🇲🇱✊🏿']
double(a)

Output

a = 
🗻b🇦🇲✊🏾
💫b🇲🇶✊🏿
🖤f🇦🇩✊🏿
🏫d🇲🇱✊🏿

ans = 
Columns 1 through 7:
 55357.   56827.   98.000   55356.   56806.   55356.   56818.
 55357.   56491.   98.000   55356.   56818.   55356.   56822.
 55357.   56740.   102.00   55356.   56806.   55356.   56809.
 55356.   57323.   100.00   55356.   56818.   55356.   56817.
Columns 8 through 10:
 9994.0   55356.   57342.
 9994.0   55356.   57343.
 9994.0   55356.   57343.
 9994.0   55356.   57343.