MATLAB: How to write 2×1 string to csv

chardlmwriteendifelseMATLABoutputstrstringswritetable

I have created a 2×1 string array which contains filenames in the first column, and a 'yes' or 'no' in the second column.

I'd like to write this information to an output format, preferrable .csv, how could I do this? Should I be converting from string to another format first?

Thanks!! My work so far:

%Create output array, table with two columns
            sz1=files; %number of rows=number files in folder
            szN=2;     %number of columns=2
            results=strings(sz1,szN);
        
            d(i).name=convertCharsToStrings(d(i).name); %convert filename to suitable format
        
            %Does it look like there is boat noise in the plot?
            answer=input('Can you see boat noise? y/n: \n', 's')
        
        
            if strcmp(answer,'y');
                %store filename in output with 'boat' in second column
                    results(row,1) = d(i).name;
                    results(row,2) = 'yesboat';
            
            elseif strcmp(answer,'n');
                %store filename in output with 'no boat' in second column
                    results(row,1) = d(i).name;
                    results(row,2) = 'noboat';
                
            else
                disp('Input must be Y or N!');
            
            end

Best Answer

You can convert to a table() object and writetable() with WriteVariableNames set to false.

Or you can do it "manually", by using fopen(), fprintf(), fclose()

Or you can

char(results(:,1) + ',' + results(:,2))

and dlmwrite() that to a .csv file, making sure you use 'delimiter', '' (that is the empty character vector)

If you were using R2019a or later (and thank you for filling in your release!), then you could use writematrix()

Related Solutions

MATLAB: Count number of rows in csv outside of matlab

Turns out this is not as easy of a question as you might think, especially if your CSV contains data that might be double-quoted and that data contains a new line character.

e.g. "This data\nhas a new line","but this doesn't"

The number of lines might not really be that important, depending on what you're trying to do. But I don't know what that is.

If you're trying to avoid having all the data in memory at one time, I suggest reading up on tabularTextDatastore, as that helps automate working with large sets of data. There's a rich set of features you can use with datastores to make working with larger datasets eaiser, tall, transform, combine. None of these assume to know the size of each table. But again, without knowing what you plan do to with those files, that's hard to say if you can use it.

---- but to answer the original question ----

If you don't have any double-quoted data, it gets a lot easier to count lines of a CSV file. This code will scan the lines without importing any of the data. (It reads the file internally, but doesn't generate any output--thats what the %*... formats are about)

fid = fopen(filename);
numLines = 0;
while ~feof(fid)
    [~,c]=textscan(fid,'%*[^\r\n]%*[\r\n]',1,'Delimiter','','Whitespace','','EndOfLine','');
    if c > 0 % if c==0, then there wasn't a line there. this may happen at the end of the file.
        numLines = numLines + 1;
    end
end
fclose(fid);

If you want the data for the lines, this newer function should help:

https://www.mathworks.com/help/matlab/ref/readlines.html

---- if you have double-quoted strings with new lines (or don't know if you do) ----

If you want to count the actual lines and not count the ones in double quoted fields, then you really need to parse each CSV line and find the fields with double-quotes, and at that point you might as well be importing the data, but if you really just want to count the parsed lines, you can do something with importOptions.

This code will import only the first variable in the table as a string, but to do that, it will still parse the file and consider the quoted data that appears later in the line. It will be slower than the method above, but robust if you have quoted data that contains newlines. It will be faster than bringing in the whole table.

opts = delimitedTextImportOptions('Delimiter',',','ExtraColumnsRule','ignore','VariableTypes',"string");
T = readtable(filename,opts);
numLines = height(T);

MATLAB: Export variable/signal

Use writematrix() in R2019a and later

writematrix(M, 'filename.txt') % M is matrix name

for older versions, you can use dlmwrite()

dlmwrite('filename.txt', M)

Best Answer

Related Solutions

MATLAB: Count number of rows in csv outside of matlab

MATLAB: Export variable/signal

Related Question