Extracting numbers from cell using regex

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kalili
kalili 2017-12-10
评论： Walter Roberson 2017-12-12
Hi,
I have the following cell:
C = {'2/6';'78/6';'982/47';'11/6'}
I would like to extract all numbers from before / and place them in a new matrix, and all numbers from after / and place them in another matrix.
The result should be something like this:
A=[2;78;982;11] B=[6;6;47;6]
How can i do this? I guess using regex would be the easiest way, but how to write it so it extracts it as explained?
Thank you for your help.

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回答（2 个）

Walter Roberson
Walter Roberson 2017-12-10
C = {'2/6';'78/6';'982/47';'11/6'};
One way:
temp = cell2mat(cellfun(@str2double,regexp(C, '(\d+)/(\d+)', 'tokens','once'),'uniform',0));
A = temp(:,1);
B = temp(:,2);
Another way:
temp = cell2mat(regexp(C, '(?<A>\d+)/(?<B>\d+)', 'names'));
A = str2double({temp.A}.');
B = str2double({temp.B}.');
Another way:
temp = cell2mat(cellfun(@str2double,regexp(C,'/','split'),'uniform',0));
A = temp(:,1);
B = temp(:,2);
Another way:
A = str2double(regexp(C,'\d+(?=/)','match','once'));
B = str2double(regexp(C,'(?<=/)\d+','match','once'));
Jos (10584)
Jos (10584) 2017-12-10
You can use cellfun to scan every string:
C = {'2/6';'78/6';'982/47';'11/6'}
V = cellfun(@(c) sscanf(c,'%f/%f'), C, 'un', 0) ;
AB = cat(2,V{:})
A = AB(1,:)
B = AB(2,:)
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kalili
kalili 2017-12-12
Hm, the data was obtained by importing an excel sheet using [~,~,C]=xlsread(filename).
Walter Roberson
Walter Roberson 2017-12-12
What shows up for
class(C{1})
When you use the third output of xlsread(), then anything that looks like a plain number will be converted to numeric but anything else will be left alone. Approximately speaking, it is like
temp = read cells as text
temp_numeric = str2double(temp);
mask = ~isnan(temp_numeric);
temp(mask) = num2cell(temp_numeric(mask))
so '2/6' should have been left alone as text because str2double() if it would be nan. Note that str2num() is not used for this purpose: str2num() would evaluate the text as an expression, getting the 0.333<etc> but that is not going to be used.

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