MATLAB: Extracting string and number pairs from a mixed string

composed stringsextract number from stringextract stringMATLABmixed stringregexpsscanf

Dear all,
I have read in material data and have gotten an array of chemical compositions of the type (chr):
'Fe61Zr8Co7Mo15B7Y2' sometimes even '(Fe0.5Co0.5)58.5Cr14Mo6C15B6Er0.5' wherein Fe and Co have a percentage of 29.25 (58.5*0.5…).
How do I extract the chemical composition so that I receive an array (or two) like
['Fe', 'Zr', 'Co', 'Mo', 'B', 'Y'; 61, 8, 7, 15, 7, 2]?
I am somehow failing to use sscanf correctly, e.g. numbers = sscanf('Fe61Zr8Co7Mo15B7Y2', '%f') won't do anything since I need to omit varying strings 🙁
Thanks a lot in advance!
Greetings
Lukas

Best Answer

The two lines marked with %%% are used to convert substrings like '(Fe0.5Co0.5)58.5' into 'Fe29.25Co29.25', after which the designator+number matching and extraction is easy:
>> str = '(Fe0.5Co0.5)58.5Cr14Mo6C15B6Er0.5';
>> baz = @(s,b)regexprep(s,'(\d+\.?\d*)','${num2str(str2double($1)*str2double(b))}'); %%%

>> tmp = regexprep(str,'\((([A-Z][a-z]*\d+\.?\d*)+)\)(\d+\.?\d*)','${baz($1,$2)}');   %%%
>> out = regexp(tmp,'([A-Z][a-z]*)(\d+\.?\d*)','tokens');
>> out = vertcat(out{:})
out = 
    'Fe'    '29.25'
    'Co'    '29.25'
    'Cr'    '14'   
    'Mo'    '6'    
    'C'     '15'   
    'B'     '6'    
    'Er'    '0.5' 
>> str2double(out(:,2)) % optional
ans =
        29.25
        29.25
           14
            6
           15
            6
          0.5
The code uses two layers of dynamic regular expression, the first calls baz for each each '(AxBy...)N' substring, then inside baz each of x, y, etc. is multiplied with N. The result is converted to char for reinsertiion.
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