MATLAB: Extracting consecutive digits using regexp

regexp

I expected

regexp('ITEM 123', '.+(\d+)', 'tokens')

to return '123'. Why does it only return '3'? What would be the correct expression?

Best Answer

These two returns "123"

%%

cac = regexp('ITEM 123', '.+?(\d+)', 'tokens' )
%%
cac = regexp('ITEM 123', '[^\d]+(\d+)', 'tokens' )

First, '.+' matches anything up til the end of the text, next it gives back just as little as needed to match '(\d+)' , which is one digit.

'.+?' matches as little as needed so that '(\d+)' is able to match the following text.

I prefer '[^\d]+(\d+)'

Or why not just

cac = regexp('ITEM 123', '\d+', 'match' )

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regexp('a == b = d','(?<!=)=(?!=)')

This looks for = that are not preceded by = and not followed by =

MATLAB: Regular expression. Are nesting of group operators supported

The Note below "Named Token Operator" indicates that the outermost will be captured, hence ABC and one token.

Note

If an expression has nested parentheses, MATLAB® captures tokens that correspond to the outermost set of parentheses. For example, given the search pattern '(and(y|rew))', MATLAB creates a token for 'andrew' but not for 'y' or 'rew'.

With string arrays, I'd recommend just creating an array of acceptable tokens:

cac = regexp("ABC", ["(ABC)","(A)", "(BC)", "(C)"], 'tokens' );
cac{:}
ans =
  1×1 cell array
    {["ABC"]}
ans =
  1×1 cell array
    {["A"]}
ans =
  1×1 cell array
    {["BC"]}
ans =
  1×1 cell array
    {["C"]}

Best Answer

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