extract coloumns from .mat file

I have a .mat file which consist of a 22253519x5 double. I need to extract first three coloums only and save them in another .mat file having 2253519x3 double data. All the rows are to be considered.

I have no clue about this. New to MATLAB. Any help would be appreciated.

Answer 1

[Walter Roberson]

The below would be easier if you only had one variable stored in the .mat file and you knew the name of the variable. The below code does not assume that there is only one variable and does not assume that the variables have any particular names; the code takes the first three columns of all of the variables that are present, and creates the new .mat file using all of the same variable names.

filename = 'YourFile.mat';
newfile = 'YourNewFile.mat';
datastruct = load(filename);
newstruct = structfun(@(M) M(:,1:3), datastruct, 'uniform', 0);
save(newfile, 'newstruct', '-struct');

[Moazza]

Thank you so much for your response . I am getting an error by running the code mentioned

Error using save Unknown command option.

Error in coloums_extract (line 6) save(newfile, 'newstruct', '-struct ');

[Stephen23]

The save option order is incorrect, '-struct' comes before the variable name:

save(newfile, '-struct','newstruct')

[Moazza]

Thank you so much . it works for me.

[Moazza]

newfile is not the one i required , it is saved as a c/h file, not containing 2253519x3 double data. please suggest .

[Walter Roberson]

What is a c/h file ?

>> some_variable = rand(22253519,5);
>> save('YourFile.mat', 'some_variable');
>> filename = 'YourFile.mat';
newfile = 'YourNewFile.mat';
datastruct = load(filename);
newstruct = structfun(@(M) M(:,1:3), datastruct, 'uniform', 0);

>> save(newfile,'-struct','newstruct')
>> whos -file YourNewFile.mat
  Name                      Size                Bytes  Class     Attributes

    some_variable      22253519x3             534084456  double

[Moazza]

thank you so much or your help :)