Calculating Linear Acceleration by subtracting gravity

QuatCalc.c

                            /* Read quaternions */
                            float q0 = float.Parse(values[3]);
                            float q1 = float.Parse(values[4]);
                            float q2 = float.Parse(values[5]);
                            float q3 = float.Parse(values[6]);

                            /* Read Gyro data */
                            Gx = float.Parse(values[7]);
                            Gy = float.Parse(values[8]);
                            Gz = float.Parse(values[9]);

                            /* Read Raw Acceleration */
                            /* Units are (m/s^2) * 0.1 */
                            ax = float.Parse(values[10]);
                            ay = float.Parse(values[11]);
                            az = float.Parse(values[12]);


                            /* Create Rotation Matrix, Android Code */
                            /* Math: See alternative expression here: https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation#Quaternion-derived_rotation_matrix */
/* http://androidxref.com/4.4.3_r1.1/xref/frameworks/native/services/sensorservice/quat.h#30 */

                            float sq_q1 = 2 * q1 * q1;
                            float sq_q2 = 2 * q2 * q2;
                            float sq_q3 = 2 * q3 * q3;
                            float q1_q2 = 2 * q1 * q2;
                            float q3_q0 = 2 * q3 * q0;
                            float q1_q3 = 2 * q1 * q3;
                            float q2_q0 = 2 * q2 * q0;
                            float q2_q3 = 2 * q2 * q3;
                            float q1_q0 = 2 * q1 * q0;

                            R[0,0] = 1 - sq_q2 - sq_q3;
                            R[0,1] = q1_q2 - q3_q0;
                            R[0,2] = q1_q3 + q2_q0;
                            R[1,0] = q1_q2 + q3_q0;
                            R[1,1] = 1 - sq_q1 - sq_q3;
                            R[1,2] = q2_q3 - q1_q0;
                            R[2,0] = q1_q3 - q2_q0;
                            R[2,1] = q2_q3 + q1_q0;
                            R[2,2] = 1 - sq_q1 - sq_q2;

                            /* Seperating gravity. remember units are (m/s^2) * 0.1 */
/* http://androidxref.com/4.4.3_r1.1/xref/frameworks/native/services/sensorservice/mat.h#203 */
/* http://androidxref.com/4.4.3_r1.1/xref/frameworks/native/services/sensorservice/GravitySensor.cpp#56 */
                            gx = R[2, 0] ;
                            gy = R[2, 1] ;
                            gz = R[2, 2] ;
                            

                            /* Removing gravity from Raw Signal */
                            /* Data Port Facing Outside */
                            ax =  -(ax - gx);
                            ay = -(ay - gy);
                            az =  -(az - gz);

                            /* Move data around for correct axes orientation in Shimmer Vs the iPhone*/
                            // If data port pointing away from hand Swap X and Y
                            gx = ax;
                            ax = ay;
                            ay = gx;