ExpressionFactor

Overview¶

The ExpressionFactor class in GTSAM is a template class designed to work with factor graphs in the context of nonlinear optimization. It represents a factor that can be constructed from a GTSAM expression, allowing for flexible and efficient computation of error terms in optimization problems.

The ExpressionFactor class allows users to define factors based on expressions in C++, that use (reverse) automatic differentiation to compute their Jacobians.

Main Methods¶

Constructor¶

The ExpressionFactor class provides a constructor that allows for the initialization of the factor with a specific expression and measurement:

  /**
   * Constructor: creates a factor from a measurement and measurement function
   *   @param noiseModel the noise model associated with a measurement
   *   @param measurement actual value of the measurement, of type T
   *   @param expression predicts the measurement from Values
   * The keys associated with the factor, returned by keys(), are sorted.
   */
  ExpressionFactor(const SharedNoiseModel& noiseModel,  //
                   const T& measurement, const Expression<T>& expression)
      : NoiseModelFactor(noiseModel), measured_(measurement) {
    initialize(expression);
  }