How to use textscan with empty char fields

Question

Joan Vazquez 2021-11-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1590189-how-to-use-textscan-with-empty-char-fields

评论： Joan Vazquez 2021-11-22

采纳的回答： Jeremy Hughes

data.txt

在 MATLAB Online 中打开

How can I use textscan with files that include these kind of lines, with empty chars?

m1 = 'HELLO,42.53,A,B,1,C';  % Only this works fine
m2 = 'HELLO,42.53,A,,1,C';
m3 = 'HELLO,42.53,A,B,1,';
m4 = 'HELLO,42.53,,,1,C';
pattern = 'HELLO%f%c%c%f%c';
delimiter = ',';
[C1, pos1] = textscan(m1, pattern, 'Delimiter', delimiter)
C1 = 1×5 cell array
    {[42.5300]}    {'A'}    {'B'}    {[1]}    {'C'}
pos1 = 19
[C2, pos2] = textscan(m2, pattern, 'Delimiter', delimiter)
C2 = 1×5 cell array
    {[42.5300]}    {'A'}    {','}    {[1]}    {'C'}
pos2 = 18
[C3, pos3] = textscan(m3, pattern, 'Delimiter', delimiter)
C3 = 1×5 cell array
    {[42.5300]}    {'A'}    {'B'}    {[1]}    {0×1 char}
pos3 = 18
[C4, pos4] = textscan(m4, pattern, 'Delimiter', delimiter)
C4 = 1×5 cell array
    {[42.5300]}    {','}    {'1'}    {0×1 double}    {0×1 char}
pos4 = 16

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Adam Danz 2021-11-18

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Since this doesn't answer the question, How can I use textscan ..., I'll leave a comment rather than an answer.

A workaround is to use strsplit and then some post-processing to convert chars to numbers.

m1 = 'HELLO,42.53,A,B,1,C';  
m2 = 'HELLO,42.53,A,,1,C';
m3 = 'HELLO,42.53,A,B,1,';
m4 = 'HELLO,42.53,,,1,C';
cleanStrFcn = @(s)[str2double(s{2}),s(3:end)];
s1 = cleanStrFcn(strsplit(m1,',','CollapseDelimiters',false))
s1 = 1×5 cell array
    {[42.5300]}    {'A'}    {'B'}    {'1'}    {'C'}
s2 = cleanStrFcn(strsplit(m2,',','CollapseDelimiters',false))
s2 = 1×5 cell array
    {[42.5300]}    {'A'}    {0×0 char}    {'1'}    {'C'}
s3 = cleanStrFcn(strsplit(m3,',','CollapseDelimiters',false))
s3 = 1×5 cell array
    {[42.5300]}    {'A'}    {'B'}    {'1'}    {0×0 char}
s4 = cleanStrFcn(strsplit(m4,',','CollapseDelimiters',false))
s4 = 1×5 cell array
    {[42.5300]}    {0×0 char}    {0×0 char}    {'1'}    {'C'}

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Answer 1

Jeremy Hughes 2021-11-18

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1590189-how-to-use-textscan-with-empty-char-fields#answer_835034

The format specifier %c always reads one character, no matter what that character is. What you likely want it %s, which reads all the characters up to the next matching delimiter.

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Stephen23 2021-11-18

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str = sprintf('%s\n', 'HELLO,42.53,A,B,1,C', 'HELLO,42.53,A,,1,C', 'HELLO,42.53,A,B,1,', 'HELLO,42.53,,,1,C')
str = 
    'HELLO,42.53,A,B,1,C
     HELLO,42.53,A,,1,C
     HELLO,42.53,A,B,1,
     HELLO,42.53,,,1,C
     '
out = textscan(str, 'HELLO,%f%s%s%f%s', 'Delimiter',',');
out{:}
ans = 4×1
   42.5300
   42.5300
   42.5300
   42.5300
ans = 4×1 cell array
    {'A'     }
    {'A'     }
    {'A'     }
    {0×0 char}
ans = 4×1 cell array
    {'B'     }
    {0×0 char}
    {'B'     }
    {0×0 char}
ans = 4×1
     1
     1
     1
     1
ans = 4×1 cell array
    {'C'     }
    {'C'     }
    {0×0 char}
    {'C'     }