How to read a selected number from a string?

Hello,

I have a string:

# Source Interval: 22.99 u (ID: 2)

and I want to read only 22.99 from this string. This number can change in different files as I have multiple files with same string but a different number ranging upto ten thousand. I tried retrieving this number using strread, but everytime I get the error Number of outputs must match the number of unskipped input fields.

Can anyone help?

Thank you

Answer 1

[Jos (10584)]

str = '# Source Interval: 22.99 u (ID: 2)'
v = strread(str,'# Source Interval: %f%*[^\n]')
% The format specifier means the following
% - '%f' - read a floating point number
% - '%*[^\n]' - ignore the rest of the string

[Novice Geek]

That works like a charm. Thank you!

Answer 2

[the cyclist]

There are multiple ways to do this. Which one is best may depend on how consistent the rest of the text is.

The regexp() command should be able to do everything you need. For example, take a look at this code:

str = '# Source Interval: 22.99 u (ID: 2)';

colonIdx = regexp(str,':');
uIdx = regexp(str,'u');
numRange = colonIdx(1)+2 : uIdx(2)-2;

num = str2num(str(numRange))

Here, I relied on the fact that your numeric string came the first occurrence of a colon and the second occurrence of the letter "u". I used regexp() to find the locations of those characters, and then the relative location of the number.

[Novice Geek]

Thank you for your reply. This seems to work. But now I get the following error:

Undefined function 'str' for input arguments of type 'double'.

I tried removing str and replaced with double and removed str2num function, there there is no error but I get the following result

num = 20 21 22 23 24

[the cyclist]

I can't be 100% sure what went wrong, without seeing your code, but here is a guess:

"str" is the variable name I gave to your string '# Source Interval: 22.99 u (ID: 2)'. If you decided to name that string something else, then you need to make that replacement everywhere in the code I posted. Otherwise, MATLAB thinks you are trying to call a function named str().