str2num(chr) converts a character array or string scalar to a numeric matrix. The input can include spaces, commas, and semicolons to indicate separate elements. If str2num cannot parse the input as numeric values, then it returns an empty matrix.
The str2num function does not convert cell arrays or nonscalar string arrays, and is sensitive to spacing around + and - operators.
str2num() contains a call to eval(), which means that if your string has the same form as an array (e.g. with semicolons) then it is simply executed and the resulting array is returned. The problems with str2num() are that it doesn’t support cell arrays, and that because it uses an eval() function, wierd things can happen if your string includes a function call. str2double() is supposedly faster as well. So the general rule seems to be, use str2double() unless you are wanting to convert a string array of numbers to a numerical array.
There is one catch though- if you are converting a single number from a string to a number, then it would SEEM like str2num() and str2double() are interchangable, drop in replacements. However, if the string is not a number, they behave differently Answer from Vignesh Murugavel on mathworks.com
MathWorks
de.mathworks.com › matlabcentral › answers › 52243-why-str2double-is-preferred-over-str2num
Why 'str2double' is preferred over 'str2num? - MATLAB Answers - MATLAB Central
It can handle all sorts of representations of numbers. For example, str2double can handle 1,000, while str2num cannot.
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Google Groups
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str2num vs str2double
I have to convert an array of around 2 millions stings (numbers) to number. I found that str2num is very slow compared to str2double. However, when I pass the array to the str2double function it return me inf.
MathWorks
mathworks.com › matlabcentral › answers › 657783-difference-between-str2num-and-str2double-for-getting-a-matrix
difference between str2num and str2double for getting a matrix - MATLAB Answers - MATLAB Central
November 22, 2020 - Personally I use str2double if I know I want a scalar, it can be more rigorous error checking, all other case I use str2num.
MathWorks
mathworks.com › matlabcentral › fileexchange › 106265-str2number-fast-replacement-for-str2num-and-str2double
str2number - Fast replacement for str2num and str2double - File Exchange - MATLAB Central
February 5, 2022 - If an input cannot be converted into a number, then the original string is returned, like the builtin str2num function, and unlike the builtin str2double function (which returns NaN for unconvertable input values).
Abeysuriya
abeysuriya.com › 2011 › 11 › 01 › matlab-str2num-str2double.html
MATLAB - str2num() vs str2double()
November 1, 2011 - str2num() contains a call to eval(), ... it uses an eval() function, wierd things can happen if your string includes a function call. str2double() is supposedly faster as well....
Octave
octave.sourceforge.io › octave › function › str2num.html
Function Reference: str2num - Octave Forge - SourceForge
Caution: As str2num uses the eval function to do the conversion, str2num will execute any code contained in the string s. Use str2double for a safer and faster conversion.
Northwestern University
ece.northwestern.edu › local-apps › matlabhelp › techdoc › ref › str2double.html
str2double (MATLAB Functions)
str2double('123.45e7') str2double('123 + 45i') str2double('3.14159') str2double('2.7i - 3.14') str2double({'2.71' '3.1415'}) str2double('1,200.34') See Also · char, hex2num, num2str, str2num
GNU Octave
docs.octave.org › v4.2.2 › String-Conversions.html
String Conversions (GNU Octave)
Caution: As str2num uses the eval function to do the conversion, str2num will execute any code contained in the string s. Use str2double for a safer and faster conversion.
YouTube
youtube.com › shorts › nu3UGL1cHGc
MATLAB: str2num (convert strings to numbers - double data type) - YouTube
This short covers the MATLAB built-in function STR2NUM() used for converting strings to doubles.STR2NUM() converts numbers that are currently a string or cha...
Published April 17, 2023
EDUCBA
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Matlab String to Number | How to Domatlab String to Number?
March 8, 2023 - Basically, now we can see how to convert a string into numbers for this, we can use a Matlab command str2num, the cell arrays, non-scalar string arrays it does not convert into numerical data type using a str2num function, and it is also sensitive spacing around to operators to avoid this error we use a str2double command.
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MathWorks
mathworks.com › matlabcentral › answers › 399831-how-to-execute-str2num-or-str2double-in-matlab
how to execute str2num or str2double in matlab? - MATLAB Answers - MATLAB Central
May 9, 2018 - I am having trouble using commands str2num. ... I used the command p=str2double(char(t)). Right now if I use str2num, a null array appears in the output whereas using str2double gives NaN in output.
Octave
octave.sourceforge.io › octave › function › str2double.html
Function Reference: str2double - Octave Forge - SourceForge
str2double can replace str2num, and it avoids the security risk of using eval on unknown data.
Tdsdesign
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Tdsdesign
So the general rule seems to be, use str2double() unless you are wanting to convert a string array of numbers to a numerical array. The str2num function does not convert cell arrays or nonscalar string arrays, and is sensitive to spacing around + and -operators.
MathWorks
mathworks.com › matlabcentral › answers › 2134576-why-is-str2num-not-recommended-when-it-is-faster-in-certain-circumstances
Why is str2num not recommended when it is faster in certain circumstances? - MATLAB Answers - MATLAB Central
July 4, 2024 - In particular, str2double cannot convert a char array and results in Inf, while str2num converts the char array without issue.