How to substitute numbers in a string with repeated strings?

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German Preciat Gonzalez
编辑： Stephen23 2017-5-9
I have many different strings with different numbers with this format:
str='A + 2 B -> D + 3 E';
I would like to replace the numbers with repeated strings so I can have
str='A + B + B -> D + E + E + E';
I did it with so many lines but it looks so ugly and I would like to ask you if you know a better way
Thanks
  1 个评论
Stephen23
Stephen23 2017-5-8
编辑：Stephen23 2017-5-8
I am sure that this could be done in just one line of code using regexprep and a dynamic replacement string. When I get back to a computer with MATLAB I will give it a try.

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采纳的回答

Stephen23
Stephen23 2017-5-9
编辑：Stephen23 2017-5-9
This is easy with a dynamic regular expression, you can adjust it to suit your needs:
>> str = 'A + 2 B -> D + 3 E';
>> regexprep(str,'(\s+)([+-])\s+(\d+)\s+([A-Z]+)','${repmat([$1,$2,$1,$4],1,str2double($3))}')
ans =
A + B + B -> D + E + E + E

更多回答（2 个）

KL
KL 2017-5-8
编辑：KL 2017-5-8
something like this?
str={'A + 2 B -> D + 3 E'};
old = {'2', '3'};
new = {'B +','E +'};
for i=1:numel(old)
str = strrep(str,old(i),new(i))
if you really want to use character array, a little tweak will do,
str=['A + 2 B -> D + 3 E'];
old = {'2', '3'};
new = {'B +','E +'};
for i=1:numel(old)
str = strrep(str,old{i},new{i})
end
end
As Stephen mentioned, regexprep makes it even more easier without a loop,
str=['A + 2 B -> D + 3 E']
old = {'2', '3'}
new = {'B +','E +'}
newStr = regexprep(str,old,new)
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German Preciat Gonzalez
German Preciat Gonzalez 2017-5-8
Thanks for the feedback, but I would like to apply a script to any formula, not just for the example I showed
Additionally, I would like to repeat the value "3 E" three times as in the example.

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Rik
Rik 2017-5-8
My first thought is using repmat, but usually when my first thought is repmat, there is a better solution using sprintf. So someone might have a way faster and more elegant solution than this.
First use isstrprop to figure out the position of the digits ( ind=isstrprop(str,'digit'); ), then loop over the numbers ( for pos=length(find(ind)):-1:1 ) to replicate the correct part.
A more important question is your source. Can you prevent your source to output this format? That would make processing with Matlab less clunky and more clear cut.

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