How to convert a text file into a table properly

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Shayan Taheri
Shayan Taheri on 11 May 2022
Answered: Chunru on 12 May 2022
Hi,
I have text file that looks like this:
time-->data1-->data2-->data3-->...
0-->1.2,2.9,3.4-->4.6,5.5,3.2-->0.1,0.1,0.9-->...
0.1-->2.2,2.4,3.4-->4.8,5.8,3.8-->0.1,0.2,0.9-->...
...
Here, --> represents a tab.
I would like to create a table out of it so that the table look like this:
0 {1.2,2.9,3.4} {4.6,5.5,3.2} {0.1,0.1,0.9} ...
0.1 {2.2,2.4,3.4} {4.8,5.8,3.8} {0.1,0.2,0.9} ...
...
To do so, I first use readtable:
T_data = readtable('my_data.txt', 'Delimiter', '\t');
This will the create a table like this:
0 {'1.2,2.9,3.4'} {'4.6,5.5,3.2'} {'0.1,0.1,0.9'} ...
0.1 {'2.2,2.4,3.4'} {'4.8,5.8,3.8'} {'0.1,0.2,0.9'} ...
...
As you can see, each element of the table is a cell containing a string. Now I use a for loop with textscan to change the string cells into numeric cells:
for row = 1:height(T_data)
for col = 2:width(T_data)
T_data{row, col} = textscan(T_data{row, col}{1}, '%f', 'Delimiter', ',');
end
end
And it does the trick, however, the second part is very slow! (A 4200*8 table took around 10 seconds.)
I was wondering if there are alternative solutions that are more eficient.
Thank you in advance.

Answers (2)

Chunru
Chunru on 12 May 2022
T = readtable('test.txt', 'Delimiter', '-->')
T = 2×4 table
time data1 data2 data3 ____ _______________ _______________ _______________ 0 {'1.2,2.9,3.4'} {'4.6,5.5,3.2'} {'0.1,0.1,0.9'} 0.1 {'2.2,2.4,3.4'} {'4.8,5.8,3.8'} {'0.1,0.2,0.9'}
for i=1:size(T,1)
for j=2:size(T,2)
T{i, j}{1} = str2num(T{i, j}{1});
end
end
T
T = 2×4 table
time data1 data2 data3 ____ ________________________ ________________________ ________________________ 0 {[1.2000 2.9000 3.4000]} {[4.6000 5.5000 3.2000]} {[0.1000 0.1000 0.9000]} 0.1 {[2.2000 2.4000 3.4000]} {[4.8000 5.8000 3.8000]} {[0.1000 0.2000 0.9000]}
  1 Comment
Shayan Taheri
Shayan Taheri on 12 May 2022
Thank you. Yes, I have also tried this solution. But the execution time is even longer for some reason!

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Chunru
Chunru on 12 May 2022
Try this:
fid = fopen('test.txt', 'r');
fgetl(fid); % skip the header
i=1;
x = [];
while ~feof(fid)
s = fgetl(fid);
tmp = textscan(s, '%f', 'Delimiter', {',', '-->'});
x = [x; tmp{1}'];
end
fclose(fid);
x
x = 2×10
0 1.2000 2.9000 3.4000 4.6000 5.5000 3.2000 0.1000 0.1000 0.9000 0.1000 2.2000 2.4000 3.4000 4.8000 5.8000 3.8000 0.1000 0.2000 0.9000

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