FIMS code club updates + add VBGF

Co-authored-by: Andrea-Havron-NOAA <Andrea-Havron-NOAA@users.noreply.github.com>

inst/include/common/model.hpp

@@ -178,6 +178,7 @@ class Model {  // may need singleton
 #endif
         MODEL_LOG << "Setting up pointer to fleet " << f->id << "."
                   << std::endl;
+        f->evaluate_length_comp();
         f->evaluate_age_comp();
         f->evaluate_index();
       }

inst/include/population_dynamics/growth/functors/VBGF.hpp

@@ -0,0 +1,66 @@
+/*
+ * This File is part of the NOAA, National Marine Fisheries Service
+ * Fisheries Integrated Modeling System project.
+ * Refer to the LICENSE file for reuse information.
+ *
+ * The purpose of this file is to declare the growth functor class
+ * which is the base class for all growth functors.
+ */
+#ifndef POPULATION_DYNAMICS_VBGF_HPP
+#define POPULATION_DYNAMICS_VBGF_HPP
+
+#include "growth_base.hpp"
+
+namespace fims_popdy {
+
+/**
+ *  @brief Von bertalanffy class that returns the length function value.
+ */
+template <typename Type>
+struct VBGF : public GrowthBase<Type> {
+
+    fims::Vector<Type> ages; /*< the vector of ages */
+    fims::Vector<Type> lengths; /*< the vector of lengths */
+    size_t a1; /*< the age at which von Bertalanffy growth starts */
+    size_t a2; /*< the age at which von Bertalanffy growth ends */
+    Type K; /*< the von Bertalanffy growth rate */
+    Type L1; /*< L1 the mean length at age a1 */
+    Type L2; /*< L2 the mean length at age a2*/
+
+    bool estimated = false;
+
+    VBGF() : GrowthBase<Type>() {}
+
+    virtual ~VBGF() {}
+
+
+    /**
+     * Computes the initial ALK.
+     */
+    virtual void Initialize(){
+        this->lengths.resize(ages.size()); 
+    }
+
+    /**
+     * Computes the length at age a from a von Bertalanffy growth function (Schnute parameterization).
+     * @param a the age at which to evaluate length
+     */
+    virtual void CalculateVBGF(size_t a){
+        lengths[0] = L1;
+        for(size_t a = 1; a < ages.size(); a++){
+            lengths[a] = L1+(L2-L1)*((1-exp(-K*(a-a1))/(1-exp(-K*(a2-a1)))));
+        }
+    }
+
+    /**
+     * @brief Returns the length at age a (in cm) from the input vector.
+     *
+     * @param a  age of the fish, the age vector must start at zero
+     */
+    virtual const Type Evaluate(const double& a) {
+        return this->CalculateVBGF(a);
+    }
+
+};
+}  // namespace fims_popdy
+#endif