How to read a specific row in a txt-file with variable row length?

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johan 2019-1-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/439906-how-to-read-a-specific-row-in-a-txt-file-with-variable-row-length

评论： johan 2019-1-16

采纳的回答： Jan

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Dear Matlab users,

Maybe someone can help me with the following:

For a project I would like to read a certain row of the txt-file constant_file_matlab.txt. In this example I would like to read the 17th row:

n=7
M = dlmread('constant_file_matlab.txt','\t',[17 0 17 n-1])

I get the following output:

M =
    -5     0    15    20    40   250     0

This is the output I would like to see, but the problem is that in some cases the length of this vector will change. I tried the following:

M = dlmread('constant_file_matlab.txt','\t',[17 0 17 end])

but is not working. Therefore my questions is: how can I read one specific row in my txt-file from the first to the last value?

However, ideally I would like to do the same as mentioned above, but with text notes at the end of each row (see txt-file: constant_file_matlab2). Is there a method to read this file with notes row by row?

Thank you.

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madhan ravi 2019-1-15

readtable() ?

johan 2019-1-16

在 MATLAB Online 中打开

Hello Madhan Ravi,

Thanks for your response.

Unfortunately, it is not returning the data in the proper way with this function. If I apply this function I get:

Warning: Variable names were modified to make them valid MATLAB identifiers. The original names are saved in the VariableDescriptions property. 
x =
  46×1 table
    x20 
    ____
      12
      17
      18
      17
      17
       0
       0
       0
       0
       0
       0
       0
       0
     104
    0.74
       1
       3
    2.15
       1
     400
       0
    0.01
     0.6
       9
       6
       4
     0.1
     2.6
     0.7
    6.85
     3.9
    0.95
       2
    1.05
    1.68
      -5
       0
      15
      20
      40
     250
       0
       1
       0
       0
       1

The readtable function creates a table by reading column orientated data.

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Answer 1

Jan 2019-1-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/439906-how-to-read-a-specific-row-in-a-txt-file-with-variable-row-length#answer_356623

编辑：Jan 2019-1-16

在 MATLAB Online 中打开

"For a project I would like to read a certain row of the txt-file constant_file_matlab.txt"

function S = ReadLineOfFile(FileName, L)
[fid, msg] = fopen(FileName, 'r');
assert(fid ~= -1, msg);
for k = 1:L-1
    fgetl(fid);  % skip one line
end
S = fgetl(fid);  % reply the L.th line:
fclose(fid)
end

Now you want to parse the line:

S = '0.10	2.60	0.70	6.85	3.90	0.95	2.00	1.05	1.68	%notes'
% Actually:
% S = ReadLineOfFile('constant_file_matlab.txt', 17)
[Value, ~, ~, nextindex] = sscanf(S, '%g ', [1, inf]);
Comment = S(nextindex:end)