Hi,

I am working with Eigen matrix/vectors passing as parameters in function. The basic structure of my code is the following:

main.cpp

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#include <iostream>
#include<Eigen/Core>
#include "f.h"

using namespace std;
using namesapce Eigen;

int main()
{
VectorXd v;
f(v);
}


f1.cpp

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#include <Eigen/Core>
#include <iostream>
#include "f1.h"

using namespace std;
using namespace Eigen;

void f1(Ref<Vector> v)
{
v = VectorXd::LinSpaced(11, 0, 10);
}


f1.h

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#ifndef F_H_INCLUDED
#define F_H_INCLUDED
#include <Eigen/Core>
include <iostream>

using namespace std;
using namespace Eigen;

void f1(Ref<Vector> v);


When I run, I have this error: Assertion failed: rows()==other.row() && cols()==other.cols(), \Library\Eigen\Eigen\src\Core\Assign.h
I suppose it's because in main I declare my vector v empty and in my function I want for example a vector of length 11.
The thing is I don't know the length of my vector in the main, I want to determine it in f1.h.
How can I do?

Thank you,

Julien

Only Matrix<> objects can be resized, so in your case the prototype of f should be:

void f(VectorXd& v);

Indeed, a Ref<VectorXd> can reference the content of a VectorXf, but also a sub-vector, like vec.segment(1,10), or a Map<VectorXd>, etc. All these objects cannot be resized.