str2double

Convert strings to double precision values

Syntax

X = str2double(str)

Description

Note

Calling string and then double is recommended over str2double because it provides greater flexibility and allows vectorization. For additional information, see Alternative Functionality.

X = str2double(str) converts the text in str to double precision values. str contains text that represents real or complex numeric values. str can be a character vector, a cell array of character vectors, or a string array. If str is a character vector or string scalar, then X is a numeric scalar. If str is a cell array of character vectors or a string array, then X is a numeric array that is the same size as str.

Text that represents a number can contain digits, a comma (thousands separator), a decimal point, a leading + or - sign, an e preceding a power of 10 scale factor, and an i or a j for a complex unit. You cannot use a period as a thousands separator, or a comma as a decimal point.

If str2double cannot convert text to a number, then it returns a NaN value.

Examples

Convert Character Vectors to Numbers

Convert character vectors that represent numbers to double precision values. You can also convert a cell array of character vectors to a numeric array of the same size.

Convert a character vector to a real number.

X = str2double('3.1416')

X = 
3.1416

Convert a character vector when it represents a number using exponential notation.

X = str2double('2.998e8')

X = 
299800000

Convert a character vector that uses a comma as the thousands separator.

X = str2double('1,200.34')

X = 
1.2003e+03

Convert a character vector to a complex number.

X = str2double('3.14 + 2.7i')

X = 
3.1400 + 2.7000i

Convert a cell array of character vectors to a numeric array.

str = {'2.718','3.1416';
       '137','0.015'};
X = str2double(str)

X = 2×2

    2.7180    3.1416
  137.0000    0.0150

Convert String Arrays to Numeric Arrays

You can convert text to numbers using the str2double function.

Create a string that represents a number. Convert it to a numeric scalar.

str = "81470.5"

str = 
"81470.5"

X = str2double(str)

X = 
8.1470e+04

Create a string array representing numbers. Convert it to a numeric array that is the same size.

str = ["292.1" "139.44" ".241" "0" "100.245"]

str = 1×5 string
    "292.1"    "139.44"    ".241"    "0"    "100.245"

X = str2double(str)

X = 1×5

  292.1000  139.4400    0.2410         0  100.2450

Input Arguments

str — Text that represents numbers

character vector | cell array of character vectors | string array

Text that represents numbers, specified as a character vector, a cell array of character vectors, or a string array.

Alternative Functionality

Update code that makes use of str2double to use string and then double instead. Using double to convert a char array produces an array of the corresponding Unicode^® values. Text in strings does not convert in this way. For example:

Not Recommended	Recommended
x = str2double('13') x = 13	x = double(string('13')) x = 13

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

The str2double function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Input text must be a string scalar or a character vector.

• Generated code always returns a complex result.

• Generated code results can differ from MATLAB^® results for misplaced commas (commas that are not used as thousands separators).

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

Usage notes and limitations:

• str must be a string array or a cell array of character vectors.

For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced before R2006a