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How to get general interval from a string with regexp

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Micke Malmström
Micke Malmström on 5 Feb 2020
I have a long string (FileName) from which I would like to extract some variables describing the X values. The string contins this format:
"... X 1.5-2.8 mm ... "
from which I successfuly can extract the range (from 1.5 to 2.8) with:
[v,vv]=regexp(FileName,[' X ([\d\.]){1,10}-([\d\.]){1,10} mm'],'tokens','match');
However, when the range includes a minus sign this does not work very well...
I've tried including the minus sign like this:
[v,vv]=regexp(FileName,[' X ([-\d\.]){1,10}-([-\d\.]){1,10} mm'],'tokens','match');
But that will for example give me (if FileName contains "-1.5-2.8") a range of from "-1.5-" to "2.8".
How can I get this line of code to work with these formats:
X 4--8 mm (where the range is from 4 to -8 mm)
X -4-8 mm
X -4--8 mm
or do I need to make a regexp for each of these cases separately?

Answers (2)

Micke Malmström
Micke Malmström on 5 Feb 2020
Seems this works ok:
[v,vv]=regexp(obj.FileName,[' X ([-\d\.]){1,10}-([-\d\.]){1,10} mm'],'tokens','match');
if ~isempty(v) % check for negative last value which gives the responce: v{1}={'2.8-','4.3'}
if strcmpi(v{1, 1}{1, 1}(end),'-')
v{1, 1}{1, 2}=['-' v{1, 1}{1, 2}];
v{1, 1}{1, 1}= v{1, 1}{1, 1}(1:end-1);
end
end

fred  ssemwogerere
fred ssemwogerere on 5 Feb 2020
Hello, making use of your string, with some modification, this should do nicely:
str="... X 1.5-2.8 mm X -2.5--3.3 mm... ";
expression = '(X \W*\d.{2})-(\W*\d.{5})';
myday=regexp(str,expression,'tokens'); % all matching strings will be stored in a cell array
% you can then use "strjoin" for each item of the cell array to get desired output for example:
val=strjoin(myday{1,1});

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