Extracting the numbers from file names and listing them in a column

Question

Babu Sankhi 2021-1-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/723233-extracting-the-numbers-from-file-names-and-listing-them-in-a-column

评论： Babu Sankhi 2021-1-22

采纳的回答： Stephen23

在 MATLAB Online 中打开

Hi all ,

I have png files like this ;

Rpma26siatBz 9.500000 Bx 0.000000mT WWait 2.000000Sec.Bzat9.5mT83.png,

Rpma26siatBz 9.500000 Bx 100.000000mT WWait 1.000000Sec.Bzat9.5mT85.png

and so on

I want to extract numbers 0.000000 from first file ,100.000000 from second file etc .and put in one column.

And again extract the numbers 2.000000 from first file,1.000000 from second file etc. and put in another column.

I tried writing the code like this but it didnt work ( I mean I got NAN)? It would be great if you share any ideas for doing it .

thank you

clear all;
close all;
clc;
listI=dir('*.png');
B=[];
for i=1:length(listI);
    n=listI(i);
    A1 =n(1:end-26);
    A2 = n(1:end-19);
    x1= str2double(A1);
    x2=str2double(A2);
    Bx=[B;(x1),(x2)];
    
    
end

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Answer 1

Stephen23 2021-1-21

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https://ww2.mathworks.cn/matlabcentral/answers/723233-extracting-the-numbers-from-file-names-and-listing-them-in-a-column#answer_603183

编辑：Stephen23 2021-1-21

在 MATLAB Online 中打开

C = {'Rpma26siatBz  9.500000 Bx 0.000000mT WWait 2.000000Sec.Bzat9.5mT83.png',...
   'Rpma26siatBz  9.500000 Bx 100.000000mT WWait 1.000000Sec.Bzat9.5mT85.png'};
M = sscanf([C{:}],'Rpma%*dsiatBz%*f Bx%fmT WWait%fSec.Bzat%*fmT%*d.png',[2,Inf]).'
M = 2×2
     0     2
   100     1

Or

W = regexp(C,'(?<=\s)\d+\.\d+(?=[A-Za-z])','match');
M = str2double(vertcat(W{:}))
M = 2×2
     0     2
   100     1

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Stephen23 2021-1-22

在 MATLAB Online 中打开

"..it does not work for these png files"

The first name has extra character/s which do not match the format string:

%...SecBzat.... 1st name
%     ^         not in format string!
%...SeBzat....  2nd and 3rd names
%...SeBzat....  format string

sscanf will stop parsing the string as soon as it reaches that 'c' character, because it does not match the format string and so does not know how to handle it. You can perform more flexible matching like this:

C = {'Rpma26siatz  -9.600000 Bx -100.000000mT Waait 600.000000SecBzat-9.6mTDAQ02.png',...
    'Rpma26siatz  -9.600000 Bx 40.000000mT Waait 2000.000000SeBzat-9.6mTDAQ45.png',...
    'Rpma26siatz  -9.600000 Bx 130.000000mT Waait 1500.000000SeBzat-9.6mTDAQ27.png'};
M = sscanf([C{:}],'%*[ A-Za-z.]%f',[6,Inf]).'
M = 3×6
           26         -9.6         -100          600         -9.6            2
           26         -9.6           40         2000         -9.6           45
           26         -9.6          130         1500         -9.6           27