Convert dataset of .mat format to .csv octave/matlab - matlab

Question

there are datasets in .mat format in the this site: http://www.cs.nyu.edu/~roweis/data.html
I want to change the format to .csv.
Can someone tell me how to change the format to create the .csv file.
Thanks!

Answer 1

Suppose that the .mat files from the site are available already. In the command window in Matlab, you may write, for example:
load('C:\Users\YourUserName\Downloads\mnist_all.mat');
to load the .mat file; the result should be a set of matrices test0, test1, ..., train0, train1 ... created in your workspace, which you want saved as CSV files. Because they're different size, you need to save one CSV per variable, e.g. (also in the command window):
csvwrite('C:\Users\YourUserName\Downloads\mnist_test0.csv', test0);
Repeat the command for each variable, and do not forget to change also the name of the output file to avoid overwriting.

Answer 2

Did you tried the csvwrite function in Matlab?
Just load your .mat files with the load function and then write them with csvwrite!

Answer 3

I do not have a Matlab license so I installed GNU Octave 4.2.1 (2017) on Windows 10 (thank you to John W. Eaton and others). I was not fully successful using the csvwrite so I used the following workaround. (BTW, I am totally incompetent in the Octave world. csvwrite worked for simple data structures).
In the Command Window I used the following two commands
load myfile.mat
save("-text","myfile.txt","variablename")
When the "myfile.mat" is loaded, the variable names for the data vectors loaded are displayed in the workspace window. This is the name(s) to use in the save command. Some .mat files will load several data structures.
The "-text" option is the default, so you may not need to include this option in the command.
The output file lists the .mat file contents in text format as single column (of potentially sequential variables). It should be easy to use you text editor to massage this data into the original matrix structure for use in whatever app you are comfortable with.

Answer 4

Had a similar issue. Needed to convert a series of .mat files that had two columns of numerical data into standard data files (ascii text). Note that I don't really ever use csv, but everything here could be adapted by using csvwrite instead of the standard save.
Using Octave 4.2.1 ....
load myfile.mat
LI = [L, I] ## L and I are column vectors representing my data
save myfile.txt LI
Note that L and I appear to be default variable names chosen by Octave for the two columns vectors in my original data file. Ideally a script that iterated over all files with the .mat extension in my directory would be ideal, but this got the job done. It saves the data as two space separated columns of data.
*** Update
The following script works on Octave 4.2.1 for a series of data files with the .mat extension that are in the same directory. It will iterate over them and write the data out to text files with the same name but with the extension .dat . Note that this is not efficient, so if you have a lot of files or if they are large it can take a while to run. I would suggest that you run it from the command line using octave mat2dat.m so you can actually watch it go.
I make no guarantees that this will work for you, but it did for me. I also am NOT proficient in Octave or Matlab, so I'm sure a better solution exists.
# mat2dat.m
dirlist = glob("*.mat")
for i=1:length(dirlist)
filename = dirlist{i,1}
load(filename, "L", "I")
LI = [L,I]
tmpname = filename(1:length(filename)-3)
txtname = strcat(tmpname, 'dat')
save(txtname, "LI")
end