How to use textscan to read my 2nd column and ignore the string or non numerical values?

Question

John Vargas 2018-8-22

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评论： Walter Roberson 2018-8-22

Hello, I have a huge data file and I was wondering if anyone could help me use textscan to only read the 2nd column but also ignore the strings. The file has this sort of format and the data keeps going.

 detector located at x,y,z = 3.97500E+03 3.97500E+03-9.95000E+01
      energy   
0000E-01   5.44426E-10 0.4254
2475E-01   1.71665E-10 0.8055
4950E-01   8.51003E-11 0.8817
7426E-01   2.09602E-10 0.6570
9901E-01   2.62823E-10 0.4473
2376E-01   3.18821E-11 0.7145
4851E-01   4.37107E-11 0.6539
7327E-01   1.34258E-10 0.6703
9802E-01   1.31857E-10 0.6663
2277E-01   4.53330E-11 0.9459
4752E-01   9.37144E-13 0.9914
7228E-01   2.99698E-10 0.9950
9703E-01   7.03990E-18 0.9950
2178E-01   5.24669E-16 0.9950
4653E-01   4.01338E-29 0.9950
7129E-01   0.00000E+00 0.0000
9604E-01   0.00000E+00 0.0000
2079E-01   0.00000E+00 0.0000
4554E-01   0.00000E+00 0.0000
7030E-01   0.00000E+00 0.0000
9505E-01   0.00000E+00 0.0000
1980E-01   9.12419E-29 0.9950
4455E-01   0.00000E+00 0.0000
6931E-01   2.43906E-25 0.9950
9406E-01   0.00000E+00 0.0000
1881E-01   0.00000E+00 0.0000
4356E-01   0.00000E+00 0.0000
6832E-01   1.86537E-12 0.9950
9307E-01   0.00000E+00 0.0000
1782E-01   2.11385E-11 0.9950
4257E-01   0.00000E+00 0.0000
6733E-01   0.00000E+00 0.0000
9208E-01   0.00000E+00 0.0000
1683E-01   0.00000E+00 0.0000
4158E-01   9.73682E-13 0.9950
6634E-01   0.00000E+00 0.0000
9109E-01   0.00000E+00 0.0000
0158E+00   0.00000E+00 0.0000
0406E+00   0.00000E+00 0.0000
0653E+00   4.94059E-40 0.9950
0901E+00   0.00000E+00 0.0000
1149E+00   0.00000E+00 0.0000
1396E+00   0.00000E+00 0.0000
1644E+00   0.00000E+00 0.0000
1891E+00   0.00000E+00 0.0000
2139E+00   0.00000E+00 0.0000
2386E+00   0.00000E+00 0.0000
2634E+00   0.00000E+00 0.0000
2881E+00   0.00000E+00 0.0000
3129E+00   0.00000E+00 0.0000
3376E+00   6.03842E-10 0.9950
3624E+00   0.00000E+00 0.0000
3871E+00   0.00000E+00 0.0000
4119E+00   0.00000E+00 0.0000
4366E+00   0.00000E+00 0.0000
4614E+00   0.00000E+00 0.0000
4861E+00   0.00000E+00 0.0000
5109E+00   0.00000E+00 0.0000
5356E+00   0.00000E+00 0.0000
5604E+00   0.00000E+00 0.0000
5851E+00   0.00000E+00 0.0000
6099E+00   0.00000E+00 0.0000
6347E+00   0.00000E+00 0.0000
6594E+00   0.00000E+00 0.0000
6842E+00   0.00000E+00 0.0000
7089E+00   0.00000E+00 0.0000
7337E+00   0.00000E+00 0.0000
7584E+00   0.00000E+00 0.0000
7832E+00   0.00000E+00 0.0000
8079E+00   0.00000E+00 0.0000
8327E+00   0.00000E+00 0.0000
8574E+00   0.00000E+00 0.0000
8822E+00   0.00000E+00 0.0000
9069E+00   0.00000E+00 0.0000
9317E+00   0.00000E+00 0.0000
9564E+00   0.00000E+00 0.0000
9812E+00   0.00000E+00 0.0000
0059E+00   0.00000E+00 0.0000
0307E+00   0.00000E+00 0.0000
0554E+00   0.00000E+00 0.0000
0802E+00   0.00000E+00 0.0000
1050E+00   0.00000E+00 0.0000
1297E+00   0.00000E+00 0.0000
1545E+00   0.00000E+00 0.0000
1792E+00   0.00000E+00 0.0000
2040E+00   0.00000E+00 0.0000
2287E+00   0.00000E+00 0.0000
2535E+00   0.00000E+00 0.0000
2782E+00   0.00000E+00 0.0000
3030E+00   0.00000E+00 0.0000
3277E+00   0.00000E+00 0.0000
3525E+00   0.00000E+00 0.0000
3772E+00   0.00000E+00 0.0000
4020E+00   0.00000E+00 0.0000
4267E+00   0.00000E+00 0.0000
4515E+00   0.00000E+00 0.0000
4762E+00   0.00000E+00 0.0000
5010E+00   0.00000E+00 0.0000
5257E+00   0.00000E+00 0.0000
5505E+00   0.00000E+00 0.0000
5752E+00   0.00000E+00 0.0000
6000E+00   0.00000E+00 0.0000
      total      2.58911E-09 0.3011
 detector located at x,y,z = 3.97500E+03 3.97500E+03-9.95000E+01
 uncollided photon flux
      energy   
0000E-01   7.06645E-15 0.9950
2475E-01   0.00000E+00 0.0000
4950E-01   0.00000E+00 0.0000

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John Vargas 2018-8-22

M1output1.txt

Here is the data.

John Vargas 2018-8-22

I am sorry, in this file, I had already removed the first two lines of strings which are:

detector located at x,y,z = 3.97500E+03 3.97500E+03-9.95000E+01 energy

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Answer 1

Star Strider 2018-8-22

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Your file is not easy to import. I’ve been working on this for a while.

Try this:

fidi = fopen('M1output1.txt','rt');
k1 = 1;
while ~feof(fidi)
    C = textscan(fidi, '%*f%f%*f', 'HeaderLines',2, 'CollectOutput',true, 'CommentStyle',{'      total', '      energy'});
    M = cell2mat(C);
    if isempty(M)
        break
    end
    D{k1,:} = M;
    fseek(fidi, 0, 0);
    k1 = k1 + 1
end
fclose(fidi);
Column2 = cell2mat(D);

The textscan format descriptor reads only Column 2, ignoring the other two columns.

The loop is necessary because you have several text lines that interrupt the ordinary file reading process, so every time textscan encounters text where it expects a numeric value, it stops, snd it is necessary to use fseek to re-start it and read the next block of numbers. Your file also does not have a valid ‘end-of-file’ indicator, so to keep the loop from becoming infinite, it is necessary to test to see if the input is empty. If it is, then the loop breaks and file reading stops. Since this does not occur until all the data have been read, no data are lost.

The cell2mat call at the end concatenates the cells in ‘D’ into a single vector.

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Star Strider 2018-8-22

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As always, my pleasure.

Yes. The asterisk between the ‘%’ and the type descriptor (here ‘f’) tells textscan to ignore that column. So to read all columns:

'%f%f%f'

to read only the first column and ignore the last two:

'%f%*f%*f'

or in a more readable (and still valid) form:

'%f %*f %*f'

and so for any other combinations you want to import or exclude.

Walter Roberson 2018-8-22

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Star Strider used a format of

'%*f%f%*f'

that says to skip the first number, read and record the second, and skip the third number.

So use %*f for any column you want to skip, and %f for any column you want to read in.

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Answer 2

Jeremy Hughes 2018-8-22

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编辑：Jeremy Hughes 2018-8-22

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I suggest trying

opts = detectImportOptions(filename)
T = readtable(filename,opts)

Also, if you want to ignore those lines:

opts = detectImportOptions(filename)
opts.ImportErrorRule = 'omitrow'
T = readtable(filename,opts)

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Answer 3

Yuvaraj Venkataswamy 2018-8-22

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You can use this,

https://in.mathworks.com/matlabcentral/answers/161434-reading-only-numeric-data-in-a-text-file

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Answer 4

Walter Roberson 2018-8-22

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You can use the CommentStyle option of textscan, specifying {'detector', 'energy'} . This will ignore the x, y, z coordinates on those lines.

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Answer 5

jonas 2018-8-22

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Here's another approach with regexprep and textscan

%%Read and remove annoying intermediate headers
str=fileread('File.txt');
str=regexprep(str,'(total|detector).*?energy','');
%%Read 2nd col
num=textscan(str,'%*f%f%*f');
out=cell2mat(num)