How to import variable names and specific data range (comma separated values) from a .txt file?

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Hi guys,
I read lots of similar questions but I cannnot solve the problem. I've downloaded Earth ephemerides from NASA JPL website(attached to this question there is the .txt file) and I need to extract only variable names line (row 23) and data from row 26 up to 29.
I want to avoid Matlab tool "import data", but rather I woulde prefer to use something like ""readtable" or similar. I tried to use readtable but I've troubles.
I tried to code something like that but it seems to not take the right lines.
clc; clear all; close all
% Ephemerides
file_name = 'Earth-Moon_sys_ephem_at_ast_epochs.txt';
opts = detectImportOptions(file_name)
opts.DataLines = [26, 29];
opts.VariableNamesLine = 34;
opts.VariableNames
opts.VariableTypes = ["double", "string", "double", "double", "double", "double", "double",...
"double", "double", "double", "double","double","double","double"];
EM_sys_eph = readtable(file_name ,opts)

Accepted Answer

Stephen23
Stephen23 on 15 Mar 2022
Edited: Stephen23 on 15 Mar 2022
Make sure you specify the delimiter and (start) Range for DETECTIMPORTOPTIONS:
file_name = 'Earth-Moon_sys_ephem_at_ast_epochs.txt';
opts = detectImportOptions(file_name, 'Range',26, 'Delimiter',',');
opts.DataLines = [26,29];
opts.VariableNamesLine = 23;
opts.VariableTypes = ["double", "string", repmat("double",1,12)];
opts.VariableNamingRule = 'preserve';
EM_sys_eph = readtable(file_name, opts)
EM_sys_eph = 4×14 table
JDTDB Calendar Date (TDB) EC QR IN OM W Tp N MA TA A AD PR __________ ________________________________ ________ __________ _________ ______ ______ __________ __________ ______ ______ _________ __________ __________ 2.4545e+06 "A.D. 2008-Mar-06 00:00:00.0000" 0.016737 1.4709e+08 0.0010567 173.6 289.27 2.4545e+06 1.1408e-05 61.112 62.808 1.496e+08 1.521e+08 3.1558e+07 2.4576e+06 "A.D. 2016-Jul-09 00:00:00.0000" 0.016735 1.4709e+08 0.0021419 173.05 289.83 2.4578e+06 1.1408e-05 184.25 184.11 1.496e+08 1.521e+08 3.1557e+07 2.4589e+06 "A.D. 2020-Mar-17 00:00:00.0000" 0.01675 1.4709e+08 0.002633 176.77 286.22 2.4589e+06 1.1407e-05 71.765 73.6 1.496e+08 1.521e+08 3.1558e+07 2.4596e+06 "A.D. 2022-Jan-21 00:00:00.0000" 0.01669 1.471e+08 0.0028082 174.65 288.52 2.4596e+06 1.1408e-05 16.87 17.437 1.496e+08 1.5209e+08 3.1558e+07
  8 Comments
Stephen23
Stephen23 on 15 Mar 2022
Edited: Stephen23 on 15 Mar 2022
If it works on your version, then:
  • go for it, use it
  • keep in mind that it might not work on other versions or OSs
The function READTABLE et al are being developed continuously, and can give different outputs for different versions (as we can see on this forum). Only you can decide if that is important for your work or not.

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More Answers (1)

Arif Hoq
Arif Hoq on 15 Mar 2022
try this:
A=readtable('Earth-Moon_sys_ephem_at_ast_epochs.txt','delimiter','tab');
B=table2cell(A(20,:));
parameter=split(B,',')';
C=table2cell(A(23:26,:));
data=split(C,',');
output=[parameter;data]

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