Column arrays measured temperature and sample time contain engine temperature measurement samples, and the time each sample was collected, respectively. assign forward diff with the forward difference. the forward difference approximation f' (x_i) is (f (x_i + 1) -f (x_i))/(x_i + 1 - x_i). if measured temperature = [91; 92; 94; 97] and sample time = [0; 1; 2; 3], then forward diff = [1; 2; 3] function forward diff = derivative approx. (measured temperature, sample time) % measured temperature: engine temperature measurements in celsius % sample time: time the sample was collected in seconds % assign forward diff with the forward difference approximation given by % (measured temperature(n + l) - measured temperature(n))/(sample time(n + 1) - sample time(n)) forward diff = measured temperature; end