How can I append table to csv file?

Hi,

I am dealing with appending problem with csv file. Briefly, I have images those come from with for loop. Every iteration I find something in image and create a new table that contains string and numerical data, but I can't merge it to csv file for every iteration. How can I do it?

Getting that error:

Undefined function 'real' for input arguments of type 'table'.

Error in dlmwrite (line 163)

str = sprintf('%.*g%+.*gi',precn,real(m(i,j)),precn,imag(m(i,j)));

Error in challenge (line 84)

dlmwrite('matrix.csv',T,'delimiter',',','-append');

My code like this:

folder = 'Downloads/challenge/';
filePattern = fullfile(folder, '*.png');
srcFiles = dir(filePattern)
numFiles = length(srcFiles)
if numFiles == 0
    message = sprintf('There are no png files are in folder:\n%s', folder);
    uiwait(warndlg(message));
else
    fprintf('There are %d files in %s:\n', numFiles, folder);
    for k = 1 : numFiles
        fprintf('    %s\n', srcFiles(k).name);
        image = uint8(imread(srcFiles(k).name));
        [T,EM] = graythresh(image);
        BW = imbinarize(image,0.3);
        [Ctrs,Radi] = imfindcircles(BW(:,:,1), [11 20],'ObjectPolarity','dark', 'Sensitivity',0.925);

        h = viscircles(Ctrs,Radi);

        T = array2table(Ctrs);
        S = srcFiles(k).name(1:end-4);
        T{:,'NewColumn'} = S;

        dlmwrite('matrix.csv',T,'delimiter',',','-append');
        
        clear T;
        clear fid;
        clear Radi;
        clear Ctrs;
        clear image; 
        clearvars -global
    end
end

Answer 1

[MJFcoNaN]

Hello,

dlmwrite cannot deal with table, but take numetric matrix or cell, such as [1 2 3] or {1,2,3}.

You may take the values of T directly, for example

dlmwrite('matrix.csv',T{:,:},'delimiter',',','-append');

PS: Since R2019a, "dlmwrite is not recommended. Use "writematrix" instead."

PS2: You may be interested in a function of "writetable" as well.

[Walter Roberson]

T contains multiple data types, you would not be able to dlmwrite T{:,:}

Use writetable. New enough versions of MATLAB support 'WriteMode', 'append' which makes the task much easier.

[melanie becker]

Hello, I'd a code that worked for matlab2022beta:

writetable(T,'outfile.txt','Delimiter',' ', 'WriteMode','append')

writetable(T,'outfile.csv','WriteMode','append')

... but now using matlab2017a I cannot use it anymore (writetable does not know append for writemode).

How I can write my test file with matlab2017a?

I use dlmwrite but I've this error: "Undefined function 'real' for input arguments of type 'string'"

My table contains both string & real,... How I can write both of them?

THanks