Inputting values from .mat file to array in C++ - c++

Question

I am trying to copy a 1100x1100 matrix from a .mat file to an array variable of type float in C++. I read online and found that the matio library is a good option. I installed their library using "make" on Ubuntu 12.04 (I followed the method given on their webpage).
However, I am unable to write code using it mainly because I am new to C++. I am using g++ to compile the file. I get errors such as "unknown reference to Mat_Open" and so on.
I did find this bit of code on the webpage:
#include <stdlib.h>
#include <stdio.h>
#include "matio.h"
int main(int argc,char **argv)
{
mat_t *matfp;
matvar_t *matvar;
matfp = Mat_Open(argv[1],MAT_ACC_RDONLY); //here argv[1] is "a.mat"?
if ( NULL == matfp )
{
fprintf(stderr,"Error opening MAT file %s0,argv[1]);
return EXIT_FAILURE;
}
matvar = Mat_VarReadInfo(matfp,"x"); // x is the variable we are trying to access?
if ( NULL == matvar )
{
fprintf(stderr,"Variable ’x’ not found, or error reading MAT file\n");
}
I have a couple of questions:
here, argv[1] corresponds to the .mat file I am trying to open right?
x in this code is the variable present in the .mat file I am trying to copy?
When I ran this code, I received errors stating - Unknown reference to Mat_Open and so on. Another couple of the same type of errors also were there.
I compiled this using : g++ abc.cpp -o test. (Followed by ./test. But I never got around to that due to the errors obtained during compilation).
How can I make it work? Is there any mistake with the code I used? Or with the compile statement I am using-maybe there are some linkers I need to use for compilation.
Thank you. Please remember that I am new to C++. Any advice would be helpful.

Answer 1

1) argv[1] - is a first parameter you put after your program call. If you want to "feel it", use debugger or code like this:
#include <iostream>
for (unsigned i = 0; i < argc; ++i)
{
std::cout << argv[i] << std::endl;
}
2) Yes, looking at http://libmatio.sourcearchive.com/documentation/1.3.4/group__MAT_g4c8205ff25c5b688a40775fbb1840b7e.html I can say, that you will read variable with name "x".
3) "undefined reference" means you need to build with matio libraries. Add something like "-lLibraryName" to your compile string. And it will have to be built.
To avoid many problems, try to install Code::Blocks, it's cross-platform and quite easy to start using C++ if you never did it before. It also supports debuggers, so you will avoid many problems quite easy.