Combining y columns of several x,y matrices into one matrix

OK, I've edited my request with more detail: I have ten (1554x2) .csv files of x,y data (I've attached eight here, for some reason couldn't load the other two!). I want to combine all the y columns of these into one matrix, with the names of each column as the first row. How do I do this please? It's OK if I don't have the names of the files included in the matrix, as long as the order in which they are added to the matrix is the same as the list of files? Thank you!

Answer 1

[Stephen23]

"How do I do this please?"

By following the guidelines in the MATLAB documentation:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

And concatenating the data vertically after the loop:

M = vertcat(C{:})

Numeric arrays do not store character data, so you cannot add headers as the first row of a numeric matrix. You could use a table, which has headers, but makes accessing the data slightly more complex. Your choice.

Note that you will have to make some decisions about how to read the files, depending on some information which you have not told us, e.g. how the files are named, what sequence you want the files imported in, what file format they use (including any delimiter, etc (I know you wrote CSV, but we regularly get people calling tab-delimited or semi-colon-delimited files "CSV" files)). Basically without an explanation of the filenames and their required order and a sample file or two, there is not much more that we can do for you. You can upload sample files by editing your question and clicking the paperclip button.

[Michel Nieuwoudt]

Thank you Stephen :). I edited my question and included some of my files. Maybe I need to rename them all as file1, file2,..file10? Best wishes, Michel

[Stephen23]

"Maybe I need to rename them all as file1, file2,..file10?"

I have no idea, because you still have not told us what order you want to read the files in. So I will guess that you want to read them in order like this:

1. UOA20_5.csv
2. UOA20_5A.csv
3. UOA20_6.csv
4. etc.

You did not give all of the filenames, which makes it a bit tricky: if all of the file suffixes are numbered from 0 to 9 exclusively (i.e. just one digit), then you could just do a character sort of the filenames to get the order that you probably want... but this is very fragile to changes in the filenames. If the filename suffix includes one or more digits, then you will need to perform an alphanumeric sort to get the order that you probably want.

You can robustly get an alphanumeric sort by downloading my FEX submission natsortfiles and using it like this:

S = dir('UOA20*.CSV');
N = natsortfiles({S.name});
C = cell(1,numel(N));
for k = 1:numel(N)
    C{k} = csvread(N{k});
end
M = vertcat(C{:});

When I run that code it creates one numeric matrix M with all of the data, and with size:

>> size(M)
ans =
   12432       2

[Michel Nieuwoudt]

Hi Stephen,Thank you so much for your answer :) and for the natsortfiles code. I will apply these! Best wishes, Michel

[Stephen23]

@Michel Nieuwoudt: I hope that it helped. Remember to accept my answer!

Answer 2

[Michel Nieuwoudt]

Thank you! have done :)