How to count how many numbers there are in a string?

Hi,

Basically I have in a script:

I need Matlab to say '3' in this example.

Any ideas?

[Guillaume]

What is the definition of 'a number'? Are 123.456, 1e7, 4*i numbers? Or is it just integers?

[Stephen23]

Here are some different ways of writing numbers: do we need to detect them all?:

• 3
• 3.14159
• +3
• 1.23E-16
• 0XF3C
• 001110101
• Inf
• two
• 4/3
• 75%

Answer 1

[Star Strider]

This works:

n = length(strsplit(st(~isletter(st))))-1;

Answer 2

[Azzi Abdelmalek]

str='a b c 45 3 2'
out=numel(regexp(str,'\d+','match'))

[John D'Errico]

As long as you don't go overboard.

str='a b c 45 3 2 1e12';
out=numel(regexp(str,'\d+','match'))
out =
     5

And does inf (or pi) count as a number? MATLAB thinks they are.

isnumeric(inf)
ans =
     1

I know, I know, I suppose pi is not a number either. It just represents a number. But the fact is, 2 just represents a number also.

[steve]

thanks for the answer. how can I explain what it means? I've never seen any of those functions and only numel and redexp come up in the help

[Ced]

That's because these are the only two functions there. You can find a list and description of the different input arguments of e.g. regexp in the documentation: Regexp Documentation