Load and do operations for multiple files in a loop

Hi everyone,

I have 306 files (1x1 struct with 2 fields: x and y) in the following format: ATA 1....306.mat. These represent coordinates from a digitized signal.

I want to read the files in MATLAB and do similar operations on all of them. The code I want to write in a loop is:

%convertstructure to table
data = struct2table(data)
%convert table to timetable
data.x= seconds (data.x)
data = table2timetable(data, 'RowTimes', x) 
% resolve potentially duplicate times in preparation for next step
data= unique(data,'sort','rows')
%resample data  (using nearest neighbour) in timetable to resolve issue of irregular times. d predefines a time step. 
d= seconds(0.0001)
data = retime(data,'regular','nearest','TimeStep',d)
save ('data')

I have made a few different unsuccesful attempts. One of them being:

filePattern = fullfile('ATA*.mat'); %the 306 files are in the following format ATA 1....306.mat
theFiles = dir(filePattern);
for k= 1:306(theFiles);
    data = load(theFiles.name); 
    data = struct2table(data);
    data.x= seconds (data.x);
    data = table2timetable(data, 'RowTimes', x);
    data= unique(data,'sort','rows');
    d= seconds(0.0001);
    data = retime(data,'regular','nearest','TimeStep',d);
    % then save as original file name
end

Your help would be much appreciated!

Regards,

Pasha

Answer 1

[Ameer Hamza]

Try something like this

filePattern = fullfile('ATA*.mat'); %the 306 files are in the following format ATA 1....306.mat
theFiles = dir(filePattern);
for k= 1:numel(theFiles)
    data = load(theFiles(k).name); 
    data = struct2table(data);
    data.x= seconds (data.x);
    data = table2timetable(data, 'RowTimes', x);
    data= unique(data,'sort','rows');
    d= seconds(0.0001);
    data = retime(data,'regular','nearest','TimeStep',d);
    % then save as original file name
    save(theFiles(k).name);
end

[Pasha]

Hi Ameer,

Thank you so much. I get an error on line 6:

Unrecognized table variable name 'x'.

I have had this error before too. Not sure why it has difficulty accessing this column of the table?

Any workarond?

Much appreciated,

Pasha

[Pasha]

So 'data' is a table which hold 'ATA*' as a structure. Pictures below.

[Ameer Hamza]

You can directly load the variable into the workspace instead of loading them into a variable. For this solution, replace the line

data = load(theFiles(k).name); 

with

load(theFiles(k).name);

However, this is not a recommended practice but will make the solution easy in this case.

An alternative method can be like this

data = load(theFiles(k).name); 
data = struct2table(data.(theFiles(k).name));

[Pasha]

Thank you Amir.

filePattern = fullfile('ATA*.mat'); %the 306 files are in the following format ATA 1....306.mat
theFiles = dir(filePattern);
for k= 1:numel(theFiles)
    load(theFiles(k).name); 
    data = struct2table(theFiles(k));
    data.x= seconds (data.x);
    data = table2timetable(data, 'RowTimes', x);
    data= unique(data,'sort','rows');
    d= seconds(0.0001);
    data = retime(data,'regular','nearest','TimeStep',d);
    % then save as original file name
    save(theFiles(k).name);
end

I rran the above code. But, there is a problem with line 5. It generates the following table which is not correct.

It runs fine if I input the file name manually e.g.

data = struct2table(ATA001);

[Ameer Hamza]

Can you share a sample .mat file with this data?

[Pasha]

Hi Ameer,

Sure! have now attached.

Regards,

Pasha

[Ameer Hamza]

Try this

filePattern = fullfile('ATA*.mat'); %the 306 files are in the following format ATA 1....306.mat
theFiles = dir(filePattern);
for k= 1:numel(theFiles)
    data = load(theFiles(k).name); 
    data = struct2table(data.(theFiles(k).name(1:end-4)));
    data.x= seconds (data.x);
    data = table2timetable(data, 'RowTimes', x);
    data= unique(data,'sort','rows');
    d= seconds(0.0001);
    data = retime(data,'regular','nearest','TimeStep',d);
    % then save as original file name
    save(theFiles(k).name);
end

[Pasha]

That works great! Thank you very much