This chapter presents the following content: Basic definitions, example of a database, typical DBMS functionality, main characteristics of the database approach, database users, workers behind the scene, . | Lecture note Data visualization - Chapter 26 Lecture 26 Recap Saving Plots Summary of Chapter 5 Introduction of Chapter 6 Function M files User defined functions are stored as M files and can be accessed by MATLAB if they are in the current folder or on MATLAB s search path Syntax of Function M file Both built in MATLAB functions and user defined MATLAB functions have the same structure Each consists of a name user provided input and calculated output. For example the function cos x is named cos takes the user input inside the parentheses in this case x calculates a result Continued . User defined functions are created in M fi les. Each must start with a function definition line that contains The word function A variable that defines the function output A function name A variable used for the input argument For example function output my_function x is the first line of the user defined function called my_function Continued . Here s an example of a very simple MATLAB function that calculates the value of a particular polynomial function output poly x This function calculates the value of a third order polynomial output 3 x. 3 5 x. 2 2 x 1 The function name is poly the input argument is x and the output variable is named output Before this function can be used it must be saved into the current folder Continued . Once the M file has been saved the function is available for use from the command window from a script M fi le or from another function You cannot execute a function M file directly from the M file itself. This makes sense since the input parameters have not been defined until you call the function from the command window or a script M file Consider the poly function just created. If in the command window we type poly 4 then MATLAB responds with ans 265 Comments As with any computer program code should be commented liberally so that it is easy to follow However in a MATLAB function the comments on the line immediately following the very first line serve a .
