Is there a function like string2double that can handle a numerical input?

Hi!

I am importing data that sometimes imports as a string, and sometimes as a number. In all cases I want a number. Is there a function like string2double that can handle a numerical input?

Right now it works like:

>> str2num('2')

ans =

     2

>> str2num(2)
Error using str2num (line 35)
Input must be a character vector or string scalar.

Ideally it would work like:

>> FunctionLikestr2num('2')

ans =

     2
>> FunctionLikestr2num(2)

ans =

     2

Thank you!

Answer 1

[Steven Lord]

First test if the input isnumeric. If it's not, try converting it from text data to a number.

[Stephen23]

+1 a much more efficient solution.

The multiple type conversions used in the accepted answer are not necessary, and likely lose data precision and slow down the code. This is a much better answer: it makes it clear what the intent is.

[Connor Brackley]

In the end I used the answer Luna submitted, but I'll flag this as the accepted answer as the loss of data is a concern.

Answer 2

[Luna]

You can do it first convert to string then convert to numeric:

str2num(string(2))
str2num(string('2'))

Both gives you numeric 2.

[Star Strider]

It is usually best to use str2double:

str2double(string(2))
str2double(string('2'))

[Connor Brackley]

Ah that is clever. That worked thanks!

[Luna]

Your welcome :)

@Star Strider you are right but I thought he wants to use str2num specifically.

[Stephen23]

@Luna: unfortunately str2num hides an eval call inside itself, which is why experienced MATLAB users try to avoid using it (especially inside loops). That is why str2double is recommended. The documentation states: "str2double Similar to str2num, but offers better performance and works with string arrays and cell arrays of character vectors."

source: https://www.mathworks.com/help/matlab/matlab_prog/converting-from-string-to-numeric.html

[Luna]

I didn't know that, thank you @Stephen Cobeldick. I noted that.

I will use recommended str2double then.