How to concatenate tables with the same number of variables but different number of rows?

I have a series of tables (AA.mat, BB,mat, CC.mat, etc...17 in total), each of them with diiferent number of rows but same number of variables (24x4, 21x4, 3x4, 29,x4, etc.). How can I merge all these tables into a single one, so it vertically concatenates rows? Thank you!

Answer 1

[Guillaume]

AA.mat, etc. are mat files not tables. Each of these file could contain any number of variables. Possibly, each of these only contain one variable, a table but that's not what you've actually described. If it is the case,

filelist = {'AA.mat', 'BB.mat', '...'}; %list of files containing the tables, possibly obtained by dir
folder = '???';  %possibly equal to pwd

fulltable = cell(size(filelist));  %cell array to receive the table contained in each file
for fileidx = 1:numel(filelist)
    filecontent = load(fullfile(folder, filelist{fileidx}));  %load file
    varlist = fieldnames(filecontent);   %get list of variables in the file
    assert(numel(varlist) == 1, 'File %s contains more than one variable', filelist{fileidx});  %check that there is only one variable in the file
    fulltable{fileidx} = filecontent.(varlist{1});  %extract the one variable in the cell array 
    assert(isa(fulltable{fileidx}, 'table'), '%s in %s is not a table', varlist{1}, filelist{fileidx}); %check that the one variable is indeed a table
end
fulltable = vertcat(fulltable{:});  %concatenate all the tables

[vicsm]

I think this will explain better my problem: how can I download all these tables automatically (instead of manually, as I have done here) and then concatenate them into one single table?

[Stephen23]

"how can I download all these tables automatically (instead of manually, as I have done here) and then concatenate them into one single table?"

By using the code in Guillaume's answer. That is exactly what it does.

If you gave us more useful information, e.g. the number of variables in each .mat file and their names, then we could tailor the code even more closely to your use case.

[vicsm]

OK, thank you. The number of variables is always 4, and the names of the variables are 'participant', 'mean_RT', 'RT_date' and 'RT_time'

[Stephen23]

@vicsm: and which of those four variables do you wish to load and concatenate?

Are these the only .mat files in that folder?

[vicsm]

I will like to concatenate the four of them into a single table.

And yes, those are the "only" 17 .mat files I have in that folder.

[Guillaume]

You need to explain better what you have. mat files, variables, and tables are completely different things. My understanding:

• you have 17 mat files (with absolutely rubbish names!)
• each of these 17 mat files contain 4 variables always named participant, mean_RT, RT_date, RT_time, possibly these variables are tables

Now, do you want to produce 17 tables, one for each file, where each table is the concatenation of the 4 variables (that's what you appear to ask)?

Or do you want to produce 4 tables, one for each variable, where each table is the concatenation of the respective variable in each file (that would make more sense)?

Or do you want to produce just 1 table, which is the concatenation of all the variables in all of the files?

Answer 2

[Stephen23]

Assuming that the data have the same class, that each .mat file contains the same four variables, and that within any one mat file they all have the same number of rows... try something like this:

D = 'path to folder where the .mat files are saved';
S = dir(fullfile(D,'*.mat'));
N = numel(S);
C = cell(N,4);
for k = 1:N
    T = load(fullfile(D,S(k).name));
    T = orderfields(T);
    C(k,:) = struct2cell(T).';
end
M = cell2mat(C)