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

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   
    1.0000E-01   5.44426E-10 0.4254
    1.2475E-01   1.71665E-10 0.8055
    1.4950E-01   8.51003E-11 0.8817
    1.7426E-01   2.09602E-10 0.6570
    1.9901E-01   2.62823E-10 0.4473
    2.2376E-01   3.18821E-11 0.7145
    2.4851E-01   4.37107E-11 0.6539
    2.7327E-01   1.34258E-10 0.6703
    2.9802E-01   1.31857E-10 0.6663
    3.2277E-01   4.53330E-11 0.9459
    3.4752E-01   9.37144E-13 0.9914
    3.7228E-01   2.99698E-10 0.9950
    3.9703E-01   7.03990E-18 0.9950
    4.2178E-01   5.24669E-16 0.9950
    4.4653E-01   4.01338E-29 0.9950
    4.7129E-01   0.00000E+00 0.0000
    4.9604E-01   0.00000E+00 0.0000
    5.2079E-01   0.00000E+00 0.0000
    5.4554E-01   0.00000E+00 0.0000
    5.7030E-01   0.00000E+00 0.0000
    5.9505E-01   0.00000E+00 0.0000
    6.1980E-01   9.12419E-29 0.9950
    6.4455E-01   0.00000E+00 0.0000
    6.6931E-01   2.43906E-25 0.9950
    6.9406E-01   0.00000E+00 0.0000
    7.1881E-01   0.00000E+00 0.0000
    7.4356E-01   0.00000E+00 0.0000
    7.6832E-01   1.86537E-12 0.9950
    7.9307E-01   0.00000E+00 0.0000
    8.1782E-01   2.11385E-11 0.9950
    8.4257E-01   0.00000E+00 0.0000
    8.6733E-01   0.00000E+00 0.0000
    8.9208E-01   0.00000E+00 0.0000
    9.1683E-01   0.00000E+00 0.0000
    9.4158E-01   9.73682E-13 0.9950
    9.6634E-01   0.00000E+00 0.0000
    9.9109E-01   0.00000E+00 0.0000
    1.0158E+00   0.00000E+00 0.0000
    1.0406E+00   0.00000E+00 0.0000
    1.0653E+00   4.94059E-40 0.9950
    1.0901E+00   0.00000E+00 0.0000
    1.1149E+00   0.00000E+00 0.0000
    1.1396E+00   0.00000E+00 0.0000
    1.1644E+00   0.00000E+00 0.0000
    1.1891E+00   0.00000E+00 0.0000
    1.2139E+00   0.00000E+00 0.0000
    1.2386E+00   0.00000E+00 0.0000
    1.2634E+00   0.00000E+00 0.0000
    1.2881E+00   0.00000E+00 0.0000
    1.3129E+00   0.00000E+00 0.0000
    1.3376E+00   6.03842E-10 0.9950
    1.3624E+00   0.00000E+00 0.0000
    1.3871E+00   0.00000E+00 0.0000
    1.4119E+00   0.00000E+00 0.0000
    1.4366E+00   0.00000E+00 0.0000
    1.4614E+00   0.00000E+00 0.0000
    1.4861E+00   0.00000E+00 0.0000
    1.5109E+00   0.00000E+00 0.0000
    1.5356E+00   0.00000E+00 0.0000
    1.5604E+00   0.00000E+00 0.0000
    1.5851E+00   0.00000E+00 0.0000
    1.6099E+00   0.00000E+00 0.0000
    1.6347E+00   0.00000E+00 0.0000
    1.6594E+00   0.00000E+00 0.0000
    1.6842E+00   0.00000E+00 0.0000
    1.7089E+00   0.00000E+00 0.0000
    1.7337E+00   0.00000E+00 0.0000
    1.7584E+00   0.00000E+00 0.0000
    1.7832E+00   0.00000E+00 0.0000
    1.8079E+00   0.00000E+00 0.0000
    1.8327E+00   0.00000E+00 0.0000
    1.8574E+00   0.00000E+00 0.0000
    1.8822E+00   0.00000E+00 0.0000
    1.9069E+00   0.00000E+00 0.0000
    1.9317E+00   0.00000E+00 0.0000
    1.9564E+00   0.00000E+00 0.0000
    1.9812E+00   0.00000E+00 0.0000
    2.0059E+00   0.00000E+00 0.0000
    2.0307E+00   0.00000E+00 0.0000
    2.0554E+00   0.00000E+00 0.0000
    2.0802E+00   0.00000E+00 0.0000
    2.1050E+00   0.00000E+00 0.0000
    2.1297E+00   0.00000E+00 0.0000
    2.1545E+00   0.00000E+00 0.0000
    2.1792E+00   0.00000E+00 0.0000
    2.2040E+00   0.00000E+00 0.0000
    2.2287E+00   0.00000E+00 0.0000
    2.2535E+00   0.00000E+00 0.0000
    2.2782E+00   0.00000E+00 0.0000
    2.3030E+00   0.00000E+00 0.0000
    2.3277E+00   0.00000E+00 0.0000
    2.3525E+00   0.00000E+00 0.0000
    2.3772E+00   0.00000E+00 0.0000
    2.4020E+00   0.00000E+00 0.0000
    2.4267E+00   0.00000E+00 0.0000
    2.4515E+00   0.00000E+00 0.0000
    2.4762E+00   0.00000E+00 0.0000
    2.5010E+00   0.00000E+00 0.0000
    2.5257E+00   0.00000E+00 0.0000
    2.5505E+00   0.00000E+00 0.0000
    2.5752E+00   0.00000E+00 0.0000
    2.6000E+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   
    1.0000E-01   7.06645E-15 0.9950
    1.2475E-01   0.00000E+00 0.0000
    1.4950E-01   0.00000E+00 0.0000

[John Vargas]

This is the code I have so far, but after running it, I realize I did not see any values when running '{S1}' and after manually deleting the first two lines in the data, I got was able to receive the data but then it stops when the data reaches another set of strings.

clear;clc; fid=fopen('M1output1.txt','r'); if fid == -1 disp('Error, check file name') else S=textscan(fid, '%f %f %f'); end fclose(fid)

[madhan ravi]

can you upload the txt file ?

[John Vargas]

Here is the data.

[John Vargas]

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

Answer 1

[Star Strider]

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.

[John Vargas]

Sweet!! thank you so much, it works. Taking it a step further, if you can help me, if I wanted to retrieve the first column or 3rd one ( or 1 and 2 ), all of this is done in the textscan format descriptor?

[Star Strider]

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]

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.

Answer 2

[Jeremy Hughes]

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)

Answer 3

[Yuvaraj Venkataswamy]

You can use this,

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

Answer 4

[Walter Roberson]

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

Answer 5

[jonas]

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)