How to extract info from a chemical formula
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Hi All, I want to break down a chemical formula into its constituents. For example: Silicon Dioxide = SiO2 I want to take the string 'SiO2' and parse it so that I know I have 1 silicon and 2 oxygens. I want to do this for more complex compounds as well, say Polyimide which is 'C22H10N2O5'. So I need to handle upper case and lower case letters, and 1 or 2 digit numbers. Any help would be much appreciated.
Pat
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Fangjun Jiang
le 12 Août 2011
Use the combination of isstrprop() and regexp() might help. You need to provide more examples and explain what you want.
str='C22H10N2O5'
num=regexp(str,'\d+','match')
isstrprop(str,'alpha')
isstrprop(str,'digit')
isstrprop(str,'upper')
One solution:
str='C22H10PuCrN2O5';
[EleList,Trash,EleEnd]=regexp(str,['[','A':'Z','][','a':'z',']?'],'match');
[Num,NumStart]=regexp(str,'\d+','match');
NumList=ones(size(EleList));
Index=ismember(EleEnd+1,NumStart);
NumList(Index)=cellfun(@str2num,Num);
3 commentaires
Fangjun Jiang
le 12 Août 2011
Please refresh my memory. Is it true that the element can only have two or one letter? If it is two-letter, is it true that the first letter is always uppercase and the second letter is lowcase?
Paulo Silva
le 12 Août 2011
look at any periodic table that you might find online, all symbols should be there
Paulo Silva
le 12 Août 2011
That's not easy to do, for example not all formulas have the constituents separated by a number, you also need to have all possible constituents in a list so you can identify them in any formula and after it check if there's a number after each constituents.
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Kelly Kearney
le 12 Août 2011
Well, assuming he's not dealing with any of those U** elements at the upper end of the periodic table, then all elements consist of either one capital letter or a capital and lowercase letter. So it should be pretty easy to pick those out. Will you always have the base formula, or will it be arranged structurally (i.e. Si(OH)4, or SiO4H4?)
Patrick Knapp
le 12 Août 2011
1 commentaire
Fangjun Jiang
le 12 Août 2011
Nice! I couldn't resist coming up with a no-loop solution. See my updated answer.
phenan08
le 26 Jan 2023
If it can help, I wrote a formula string parser to determine the composition of a molecule, element by element.
It is possible to use semi-developped formulas, and the script returns 4 outputs: the raw molecular formula, the composition table (the different elements with their counts), the average MW and the monoisotopic mass.
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