Access and extract table array using for loop

I have this table

tt = edfread('example.edf')

tt = 6×2 timetable
    Record Time          ECG               ECG2      
    ___________    _______________    _______________

    0 sec          {1280×1 double}    {1280×1 double}
    10 sec         {1280×1 double}    {1280×1 double}
    20 sec         {1280×1 double}    {1280×1 double}
    30 sec         {1280×1 double}    {1280×1 double}
    40 sec         {1280×1 double}    {1280×1 double}
    50 sec         {1280×1 double}    {1280×1 double}

and I need to extract (or access) the data using "for loop". For example, from "ECG", we can extract the data from 0 sec, 10 sec, 20 sec, etc. without typing the code one-by-one manually. What should I do? Thank you.

Answer 1

[VBBV]

tt = edfread('example.edf')

tt = 6×2 timetable
    Record Time          ECG               ECG2      
    ___________    _______________    _______________

    0 sec          {1280×1 double}    {1280×1 double}
    10 sec         {1280×1 double}    {1280×1 double}
    20 sec         {1280×1 double}    {1280×1 double}
    30 sec         {1280×1 double}    {1280×1 double}
    40 sec         {1280×1 double}    {1280×1 double}
    50 sec         {1280×1 double}    {1280×1 double}

tt = timetable2table(tt);
tt.Properties.VariableNames = {'Time','ECG','EEG2'};
for k = 1:length(tt.ECG)
    fprintf('ECG Data at %s is\n',[tt.Time(k)])
    cell2mat(tt.ECG(k))
end

ECG Data at 0 sec is

ans = 1280×1

-0.1126 -0.0915 -0.0774 -0.0422 -0.0070 -0.0070 0.0352 0.0704 0.0845 0.1197

ECG Data at 10 sec is

ans = 1280×1

-0.2041 -0.2112 -0.1830 -0.1549 -0.1478 -0.1337 -0.0915 -0.0493 -0.0352 0.0423

ECG Data at 20 sec is

ans = 1280×1

-0.0281 -0.0493 -0.0352 -0.0352 -0.0563 -0.0704 -0.0704 -0.0985 -0.0774 -0.0563

ECG Data at 30 sec is

ans = 1280×1

-0.0633 -0.0845 -0.0845 -0.0915 -0.0915 -0.0985 -0.0845 -0.0985 -0.0985 -0.0985

ECG Data at 40 sec is

ans = 1280×1

-0.0774 -0.0493 -0.0281 0.0000 0.0282 0.0986 0.1267 0.1549 0.1971 0.2253

ECG Data at 50 sec is

ans = 1280×1

-0.0774 -0.0633 -0.0704 -0.0704 -0.0422 -0.0563 -0.0422 -0.0704 -0.0704 -0.0774

[Edoardo]

How about to access the data horizontally, for example, I have not only ECG1 and ECG2, but also ECG3, ECG4, ..., ECG100, etc. How to do it?

[VBBV]

tt = edfread('example.edf')

tt = 6×2 timetable
    Record Time          ECG               ECG2      
    ___________    _______________    _______________

    0 sec          {1280×1 double}    {1280×1 double}
    10 sec         {1280×1 double}    {1280×1 double}
    20 sec         {1280×1 double}    {1280×1 double}
    30 sec         {1280×1 double}    {1280×1 double}
    40 sec         {1280×1 double}    {1280×1 double}
    50 sec         {1280×1 double}    {1280×1 double}

tt = timetable2table(tt);
tt.Properties.VariableNames = {'Time','ECG1','ECG2'};

%%% for large number of variables %%%
%J = 1
% fprintf(repmat('%s Data ',1,100) \n', char(tt.Properties.VariableNames(J+1)),char(tt.Properties.VariableNames(J+2)), ... so on)
fprintf('%s Data  %s Data \n', char(tt.Properties.VariableNames(2)),char(tt.Properties.VariableNames(3)))

ECG1 Data  ECG2 Data 

for k = 1:length(tt.ECG1)
    fprintf('at %s is\n',tt.Time(k))
    [cell2mat(tt.ECG1(k)) cell2mat(tt.ECG2(k))]
end

at 0 sec is

ans = 1280×2

-0.1126 -0.0070 -0.0915 -0.0070 -0.0774 -0.0070 -0.0422 -0.0000 -0.0070 -0.0000 -0.0070 -0.0070 0.0352 -0.0000 0.0704 0.0070 0.0845 -0.0000 0.1197 -0.0070

at 10 sec is

ans = 1280×2

-0.2041 0.0559 -0.2112 0.0629 -0.1830 0.0559 -0.1549 0.0699 -0.1478 0.0489 -0.1337 0.0559 -0.0915 0.0489 -0.0493 0.0699 -0.0352 0.0839 0.0423 0.0559

at 20 sec is

ans = 1280×2

-0.0281 0.0280 -0.0493 0.0349 -0.0352 0.0280 -0.0352 0.0280 -0.0563 0.0210 -0.0704 -0.0000 -0.0704 -0.0000 -0.0985 0.0210 -0.0774 0.0210 -0.0563 0.0210

at 30 sec is

ans = 1280×2

-0.0633 -0.0140 -0.0845 -0.0280 -0.0845 -0.0280 -0.0915 -0.0210 -0.0915 -0.0140 -0.0985 -0.0280 -0.0845 -0.0140 -0.0985 -0.0280 -0.0985 -0.0070 -0.0985 -0.0280

at 40 sec is

ans = 1280×2

-0.0774 0.0349 -0.0493 0.0210 -0.0281 0.0210 0.0000 0.0280 0.0282 0.0349 0.0986 0.0210 0.1267 0.0210 0.1549 0.0280 0.1971 0.0280 0.2253 -0.0000

at 50 sec is

ans = 1280×2

-0.0774 -0.0280 -0.0633 -0.0419 -0.0704 -0.0070 -0.0704 -0.0000 -0.0422 -0.0000 -0.0563 -0.0000 -0.0422 -0.0000 -0.0704 -0.0070 -0.0704 -0.0070 -0.0774 -0.0140

[Edoardo]

I mean if I have something like this

how do I access all the data from ECG1 to ECG16 without inputting one-by-one?

[VBBV]

You can access all table data without inputting one by one as shown below

tt = edfread('example.edf');
tt = timetable2table(tt);
tt.Properties.VariableNames = {'Time','ECG1','ECG2'};
%%% for large number of variables %%%
% fprintf(repmat('%s Data',1,100) \n', string(tt.Properties.VariableNames(2:end)))
fprintf('%s Data  %s Data \n', string(tt.Properties.VariableNames(2:end)))

ECG1 Data  ECG2 Data 

for k = 1:length(tt.ECG1)    
    fprintf('at %s is\n',tt.Time(k))
    % access all data from table without inputting one by one
    Data = cell2mat(table2cell(tt(k,2:end)))     
end

at 0 sec is

Data = 1280×2

-0.1126 -0.0070 -0.0915 -0.0070 -0.0774 -0.0070 -0.0422 -0.0000 -0.0070 -0.0000 -0.0070 -0.0070 0.0352 -0.0000 0.0704 0.0070 0.0845 -0.0000 0.1197 -0.0070

at 10 sec is

Data = 1280×2

-0.2041 0.0559 -0.2112 0.0629 -0.1830 0.0559 -0.1549 0.0699 -0.1478 0.0489 -0.1337 0.0559 -0.0915 0.0489 -0.0493 0.0699 -0.0352 0.0839 0.0423 0.0559

at 20 sec is

Data = 1280×2

-0.0281 0.0280 -0.0493 0.0349 -0.0352 0.0280 -0.0352 0.0280 -0.0563 0.0210 -0.0704 -0.0000 -0.0704 -0.0000 -0.0985 0.0210 -0.0774 0.0210 -0.0563 0.0210

at 30 sec is

Data = 1280×2

-0.0633 -0.0140 -0.0845 -0.0280 -0.0845 -0.0280 -0.0915 -0.0210 -0.0915 -0.0140 -0.0985 -0.0280 -0.0845 -0.0140 -0.0985 -0.0280 -0.0985 -0.0070 -0.0985 -0.0280

at 40 sec is

Data = 1280×2

-0.0774 0.0349 -0.0493 0.0210 -0.0281 0.0210 0.0000 0.0280 0.0282 0.0349 0.0986 0.0210 0.1267 0.0210 0.1549 0.0280 0.1971 0.0280 0.2253 -0.0000

at 50 sec is

Data = 1280×2

-0.0774 -0.0280 -0.0633 -0.0419 -0.0704 -0.0070 -0.0704 -0.0000 -0.0422 -0.0000 -0.0563 -0.0000 -0.0422 -0.0000 -0.0704 -0.0070 -0.0704 -0.0070 -0.0774 -0.0140

Answer 2

[Ran Yang]

See How to work with tables and timetables.

You can call everything in the ECG column using {:} and then concatenate it. Note the curly brackets.

data = cat(1, tt.ECG{:});

You can also specify a subset of rows (e.g. 0 sec, 20 sec, 40 sec) in the same way you would index a regular array.

subdata = cat(1, tt.ECG{1:2:5});

[Edoardo]

I mean using the for loop command, so that for example I have the data with more than 60 seconds I can access it conveniently without writing the code one-by-one

Answer 3

[Stephen23]

"I need to extract (or access) the data using "for loop". For example, from "ECG", we can extract the data from 0 sec, 10 sec, 20 sec, etc. without typing the code one-by-one manually."

You can use curly-brace indexing:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-table.html

Note that the example numeric data is nested in cell arrays in a table:

T = edfread('example.edf')

T = 6×2 timetable
    Record Time          ECG               ECG2      
    ___________    _______________    _______________

    0 sec          {1280×1 double}    {1280×1 double}
    10 sec         {1280×1 double}    {1280×1 double}
    20 sec         {1280×1 double}    {1280×1 double}
    30 sec         {1280×1 double}    {1280×1 double}
    40 sec         {1280×1 double}    {1280×1 double}
    50 sec         {1280×1 double}    {1280×1 double}

for ii = 1:height(T)
    for jj = 1:width(T)
        V = T{ii,jj}{:}
    end
end

V = 1280×1

-0.1126 -0.0915 -0.0774 -0.0422 -0.0070 -0.0070 0.0352 0.0704 0.0845 0.1197

V = 1280×1

-0.0070 -0.0070 -0.0070 -0.0000 -0.0000 -0.0070 -0.0000 0.0070 -0.0000 -0.0070

V = 1280×1

-0.2041 -0.2112 -0.1830 -0.1549 -0.1478 -0.1337 -0.0915 -0.0493 -0.0352 0.0423

V = 1280×1

0.0559 0.0629 0.0559 0.0699 0.0489 0.0559 0.0489 0.0699 0.0839 0.0559

V = 1280×1

-0.0281 -0.0493 -0.0352 -0.0352 -0.0563 -0.0704 -0.0704 -0.0985 -0.0774 -0.0563

V = 1280×1

0.0280 0.0349 0.0280 0.0280 0.0210 -0.0000 -0.0000 0.0210 0.0210 0.0210

V = 1280×1

-0.0633 -0.0845 -0.0845 -0.0915 -0.0915 -0.0985 -0.0845 -0.0985 -0.0985 -0.0985

V = 1280×1

-0.0140 -0.0280 -0.0280 -0.0210 -0.0140 -0.0280 -0.0140 -0.0280 -0.0070 -0.0280

V = 1280×1

-0.0774 -0.0493 -0.0281 0.0000 0.0282 0.0986 0.1267 0.1549 0.1971 0.2253

V = 1280×1

0.0349 0.0210 0.0210 0.0280 0.0349 0.0210 0.0210 0.0280 0.0280 -0.0000

V = 1280×1

-0.0774 -0.0633 -0.0704 -0.0704 -0.0422 -0.0563 -0.0422 -0.0704 -0.0704 -0.0774

V = 1280×1

-0.0280 -0.0419 -0.0070 -0.0000 -0.0000 -0.0000 -0.0000 -0.0070 -0.0070 -0.0140