Writing and reading data from files

Here we will use the it_file class to store some data. The program write_it_file.cpp looks as follows:

#include <itpp/itcomm.h>

using namespace itpp;

int main() {
        // Declare the it_file class
        it_file ff;

        // Open a file with the name "it_file_test.it"
        ff.open ( "it_file_test.it" );

        // Create some data to put into the file
        vec a = linspace ( 1, 20, 20 );

        // Put the variable a into the file. The Name("a") tells the file class
        // that the next variable shall be named "a".
        ff << Name ( "a" ) << a;

        // Force the file to be written to disc. This is useful when performing
        // iterations and ensures that the information is not stored in any cache
        // memory. In this simple example it is not necessary to flush the file.
        ff.flush();

        // Close the file
        ff.close();

        // Exit program
        return 0;
}

When you run this program you will obtain a file called it_file_test.it in your current directory. You can read the file into Matlab/Octave to view the data by using the following commands:

itload('it_file_test.it')
figure(1); clf;
plot(a)

Note: Make sure that $PREFIX/share/itpp is in your Matlab/Octave path and that you run the code above from the directory where it_file_test.it is located ($PREFIX is the IT++ installation prefix; /usr/local by default).

The IT++ program read_it_file.cpp that reads the file and prints its content can look like this:

Here is the output of the program:

a = [1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20]