Basics of MATLAB and Beyond

X = QUADRATIC(A,B,C) returns the two roots of thequadratic equationy = A*x^2 + B*x + C.The roots are contained in X = [X1 X2].matlab only echoes the comment lines that are contiguous; the first noncommentline, in this case the blank line before the signature, tells matlabthat the help comments have ended. The first line of the help commentsis searched and, if successful, displayed when you type a lookforcommand.Comment lines can appear anywhere in the body of an m-file. Commentscan be put at the end of a line of code:rootdisc = sqrt(b.^2 - delta); % Root of the discriminantBlank lines can appear anywhere in the body of an m-file. Apart fromending the help comment lines in a function, blank lines are ignored.8.3 Flow Controlmatlab has four kinds of statements you can use to control the flowthrough your code:if, else and elseif execute statements based on a logical testswitch, case and otherwise execute groups of statements based ona logical testwhile and end execute statements an indefinite number of times,based on a logical testfor and end execute statements a fixed number of timesIf, Else, ElseifThe basic form of an if statement is:if teststatementsendThe test is an expression that is either 1 (true) or 0 (false). Thestatements between the if and end statements are executed if thetest is true. If the test is false the statements will be ignored andexecution will resume at the line after the end statement. The testexpression can be a vector or matrix, in which case all the elementsmust be equal to 1 for the statements to be executed. Further testscan be made using the elseif and else statements.Exercise 2 Write a function m-file that takes a vector input andreturns 1 if all of the elements are positive, −1 if they are all negative,and zero for all other cases. Hint: Type help all. (Answeron page 183.)c○ 2000 by CRC Press LLC