combining different csv files from a folder into one matrix

Hello, I have 800 files with 1554rows and 2columns so (1554x2) , that I'd like to read from a folder and then combine them into a large matrix of 1554x801. The first column is common to each file, and so I'd like to set only the first column in the final matrix as the same column of all the files, and then the subsequent columns as the second column of each of the 800 files. I hope this makes sense.

Example:

A.csv=[1 2; 4 5] and B.csv=[1 8 ;4 7], C.csv=[1 6;4 10]

I'd like to combine these into

Combined=[1 2 8 6; 4 5 7 10]

Would anyone possibly have a code for this? I'm new to Matlab and have tried a number of codes that merge files. but they stack them horizontally so I get

[1 2;4 5;1 8;4 7;1 6;4 10].

Thank you!

Answer 1

[Stephen23]

"Is theremaybe a way to list the filenames in the same order, then add them afterwards as the top row to the table?"

You could use a table:

O = {'ReadVariableNames',false};
D = '.'; % path to the directory where the files are saved.
S = dir(fullfile(D,'*.csv'));
for k = 1:numel(S)
    U = readtable(fullfile(D,S(k).name),O{:});
    [~,N] = fileparts(S(k).name);
    U.Properties.VariableNames = {'time',N};
    if k==1
        T = U;
    else
        T = join(T,U);
    end
end

Giving (the test files are attached to this answer):

>> T
T = 
    time    A    B    C 
    ____    _    _    __
    1       2    8     6
    4       5    7    10
>> T.B
ans =
     8
     7

[Michel Nieuwoudt]

Hi Stephen,

This is exactly what I needed. Thank you so so much!

Best wishes,

Michel

Answer 2

[KSSV]

csvfiles = dir('*.csv') ; 
iwant = zeros(1554,801) ; 
for i = 1:length(csvfiles)
    data = csvread(csvfiles(i).name) ; 
    if i == 1
        iwant(:,1:2) = data ;
    else
        iwant(:,i+1) = data(:,2) ;
    end
end

[Michel Nieuwoudt]

Dear KSSV, Thank you!

I tried to run it, but get the following error message:

Error using dlmread (line 147)

Mismatch between file and format string.

Trouble reading 'Numeric' field from file (row number 2, field number 1) ==> ;6.553229e+003\n

Error in csvread (line 48)

m=dlmread(filename, ',', r, c);

Error in Combinenew (line 4)

data = csvread(csvfiles(i).name ) ;

I checked the numbers in the files and they are in scientitic format, with no \n at the end of the number. Would you now how to solve this?

Thank you :)

[KSSV]

It sems you have some header lines in your file? Attach one file.

[Michel Nieuwoudt]

I don't think so, but here are two of the files :)

[KSSV]

Both the files are working fine with csvread, no error here. Try using load instead of csvread.

[Michel Nieuwoudt]

It worked a treat.

Thank you so, so much KSSV!

[Michel Nieuwoudt]

Would it be possible to have the filenames included at the top of each column too?

[KSSV]

It can be but...why unnecessary complexity? You should take it as a table.

[Michel Nieuwoudt]

I need to know the filename that each column represents. Is theremaybe a way to list the filenames in the same order, then add them afterwards as the top row to the table?