How to read CSV file and save the result to another CSV file

Hello.

I have several CSV files.

After processing each CSV file, I want to save each CSV file to other name using for loop.

The names of input file are different (bend1.csv, walk2.csv, jogging2.csv, ....)

clear all
close all

X = csvread('bend1.csv');
X = X(:,1:28);

data = X';

% After processing......


% I want to each Y matrix to CSV files
Y = Phi_NuMax * X';

csvwrite('/result/bend1.csv', Y);

[Akira Agata]

You mean, you have many CSV files in one folder and want to save in another folder with the same file name after applying some processing?

[Kong]

YES! I want to do it.

Answer 1

[Peng Li]

a simple structure:

outDir = yourDestination.
allCsvFiles = dir(fullfile(yourDirectory, '.*csv'));
for iA = 1:length(allCsvFiles)
    curFile = allCsvFiles(iA).name;
    
    yourTable = readtable(fullfile(yourDirectory, curFile));
    % your process
    
    writetable(fullfile(outDir, curFile), yourTable);
end

[Kong]

Thank you so much.

I don't know what is curFile.

Could you check my code?

clear all
close all

outDir = '/';
allCsvFiles = dir(fullfile('/', '.*csv'));
for iA = 1:length(allCsvFiles)
    curFile = allCsvFiles(iA).name;
    
    yourTable = readtable(fullfile('/', curFile));
    % your process
    curFile = curFile(:,1:28);

    data = curFile';

    
    opt.init_num_secants = 28;
    idx1 = random('unid',size(data, 2), opt.init_num_secants, 1);
    idx2 = random('unid',size(data, 2), opt.init_num_secants, 1);
    secants = data(:, idx1)-data(:, idx2);
    D1 = abs(secants);


    numSecants = size(X,2);


    options.landmarks = 1:28; 
    [geo] = IsomapII(D1, 'k', 3, options); 
    secants = geo/norm(geo,2);

    
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    %%%%%Parameter setting
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    opt.outer_iterations = 1000;
    
    switch 'l-bfgs'
        case 'grad'
            opt.linear_solver = 'grad';
            opt.tau = 1e-1; % gradient step size
            opt.inner_iterations = 10;
            opt.beta1 = 1e-1; opt.beta2 = 1e-1; %penalty parameters
            opt.eta1 = 1; opt.eta2 = 1; %lagrangian update
        case 'cgs'
            opt.linear_solver = 'cgs';
            opt.linear_iterations = 10;
            opt.inner_iterations = 1;
            opt.beta1 = 1; opt.beta2 = 1; %penalty parameters
            opt.eta1 = 1.618; opt.eta2 = 1.618; %lagrangian update
        case 'l-bfgs'
            opt.linear_solver = 'l-bfgs';
            opt.linear_iterations = 3;
            opt.lbfgs_rank = 5;
            opt.inner_iterations = 1;
            opt.beta1 = 1; opt.beta2 = 1; %penalty parameters
            opt.eta1 = 1.618; opt.eta2 = 1.618; %lagrangian update
    end
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    %%End parameters
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    delta = -3000; %max-margin parameter

    funA = @(z) funA_secants_WY(z, secants);
    funAT = @(z) funAT_secants_WY(z, secants);

    b = ones(numSecants, 1);

    ticID = tic;
    [P, L, q, Lambda, w] = NuMax(funA, funAT, b, delta, opt);
    toc(ticID);


    [U, S, V] = svd(P);
    r = rank(P);
    U1 = U(:, 1:r);
    U1 = (U1 - min(U1(:)))/(max(U1(:))-min(U1(:)));

    Phi_NuMax = (U(:, 1:r)*(S(1:r, 1:r).^(1/2)))';
    
    Y = Phi_NuMax * X';
    Y = Y';
    
    writetable(fullfile(outDir, curFile), yourTable);
end

[Peng Li]

you should work with yourTable after loading. if you check variables in memory, youTable is the data you load. curFile is just the file name of the current file under processing.

[Kong]

Thank you so much.

When I just used the code, there is no file. Could you explain is?

clear all
close all

outDir = '/';
allCsvFiles = dir(fullfile('/', '.*csv'));
for iA = 1:length(allCsvFiles)
    curFile = allCsvFiles(iA).name;
    
    yourTable = readtable(fullfile('/', curFile));
    % your process
end

[Peng Li]

Where did you save your csv file? using the directory to replace '/' when you call dir.

As you are saving the csv files with the same name, you don't want to replace your orignal files. So better designate a different directory for outDir.

[Kong]

I am sorry to bother you.

I changed outDir. When I tried to read each CSV file, what is Table?

yourTable is empty.

[Peng Li]

In the dir call, replace .*csv with *.csv.

Sorry it was my mistake that I had this typo in my example lol