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diff --git a/src/msvmmaj_matrix.c b/src/msvmmaj_matrix.c
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+/**
+ * @file msvmmaj_matrix.c
+ * @author Gertjan van den Burg
+ * @date August, 2013
+ * @brief Functions facilitating matrix access
+ *
+ * @details
+ * The functions contained in this file are used when
+ * accessing or writing to matrices. Seperate functions
+ * exist of adding and multiplying existing matrix
+ * elements, to ensure this is done in place.
+ *
+ */
+
+#include "msvmmaj_matrix.h"
+#include "util.h"
+
+/**
+ * @brief Set element of matrix 
+ *
+ * @details
+ * Row-Major order is used to set a matrix element. Since matrices
+ * of type double are most common in MSVMMaj, this function only
+ * deals with that type.
+ *
+ * @param[in] 	M 	matrix to set element of
+ * @param[in] 	cols 	number of columns of M
+ * @param[in] 	i 	row index of element to write to
+ * @param[in] 	j 	column index of element to write to
+ * @param[out] 	val 	value to write to specified element of M
+ */
+void matrix_set(double *M, long cols, long i, long j, double val)
+{
+	M[i*cols+j] = val;
+}
+
+/**
+ * @brief Retrieve value from matrix
+ * 
+ * @details
+ * Return a value from a matrix using row-major order.
+ *
+ * @param[in] 	M 	matrix to retrieve value from
+ * @param[in] 	cols 	number of columns of M
+ * @param[in] 	i 	row index (starting from 0)
+ * @param[in] 	j 	column index (starting from 0)
+ * @returns 		matrix element at (i, j)	
+ */
+double matrix_get(double *M, long cols, long i, long j)
+{
+	return M[i*cols+j];
+}
+
+/**
+ * @brief Add value to matrix element
+ *
+ * @details
+ * This function is added to efficiently add values to matrix
+ * elements, without having to use get and set methods.
+ *
+ * @param[in] 	M 	matrix
+ * @param[in] 	cols 	number of columns of M
+ * @param[in] 	i  	row index (starting from 0)
+ * @param[in] 	j 	column index (starting from 0)
+ * @param[in] 	val 	value to add to matrix element (i, j)
+ */
+void matrix_add(double *M, long cols, long i, long j, double val)
+{
+	M[i*cols+j] += val;
+}
+
+/**
+ * @brief Multiply matrix element by value
+ * 
+ * @details
+ * This function is added to efficiently multiply a matrix element
+ * by a certain value, without having to use get and set methods.
+ *
+ * @param[in] 	M 	matrix
+ * @param[in] 	cols 	number of columns of M
+ * @param[in] 	i 	row index (starting from 0)
+ * @param[in] 	j 	column index (starting from 0)
+ * @param[in] 	val 	value to multiply matrix element (i, j) with
+ */
+void matrix_mul(double *M, long cols, long i, long j, double val)
+{
+	M[i*cols+j] *= val;
+}
+
+/**
+ * @brief Set element of 3D matrix
+ *
+ * @details
+ * Set an element of a 3D matrix using row-major order. 
+ *
+ * @param[in] 	M 	matrix
+ * @param[in] 	N2 	second dimension of M
+ * @param[in] 	N3 	third dimension of M
+ * @param[in] 	i 	index along first dimension
+ * @param[in] 	j 	index along second dimension
+ * @param[in] 	k 	index along third dimension
+ * @param[in] 	val 	value to set element (i, j, k) to
+ *
+ * See:
+ * http://en.wikipedia.org/wiki/Row-major_order
+ */
+void matrix3_set(double *M, long N2, long N3, long i, long j, 
+		long k, double val)
+{
+	M[k+N3*(j+N2*i)] = val;
+}
+
+/**
+ * @brief Get element of 3D matrix
+ *
+ * @details
+ * Retrieve an element from a 3D matrix.
+ *
+ * @param[in] 	M 	matrix
+ * @param[in] 	N2 	second dimension of M
+ * @param[in] 	N3 	third dimension of M
+ * @param[in] 	i 	index along first dimension
+ * @param[in] 	j 	index along second dimension
+ * @param[in] 	k 	index along third dimension
+ * @returns 		value at the (i, j, k) element of M
+ */
+double matrix3_get(double *M, long N2, long N3, long i, long j,
+		long k)
+{
+	return M[k+N3*(j+N2*i)];
+}
+
+/**
+ * @brief print a matrix
+ * 
+ * @details
+ * Debug function to print a matrix
+ *
+ * @param[in] 	M 	matrix
+ * @param[in] 	rows 	number of rows of M
+ * @param[in] 	cols 	number of columns of M
+ */
+void print_matrix(double *M, long rows, long cols)
+{
+	long i, j;
+
+	for (i=0; i<rows; i++) {
+		for (j=0; j<cols; j++)
+			note("%8.8f ", matrix_get(M, cols, i, j));
+		note("\n");
+	}
+	note("\n");
+}