MatLab – Palm Chapter 4, Part 3For and While Loops.ppt

4/5/2004 ENGR 111A - Spring 2004 MatLab – Palm Chapter 4, Part 3For and While Loops Class 11.1 Palm Ch 4.5 RAT 11.1 As in INDIVIDUAL you have 2 minutes to answer the following question. What is the FINAL value assigned to y in the following segment of MATLAB code? x = 0; while x 5 y = sqrt(x); x = x + 1; end When asked, you have 30-seconds to submit your paper. Answer: y = 2 Learning Objectives Students should be able to: Understand Matlab iteration structures:for … end Loops while … end Loops Identify Implied loops Recognize these structures as repetition (or iteration) structures. Develop flow (logic) diagrams for combinations of branching and looping structures LOOPS A LOOP is a structure for repeating (iterating) a block of code. MATLAB uses two types of loops. for loop: number of passes known a priori (p. 210). while loop: loop terminates when a specified condition is satisfied (p. 221). for LOOPS SYNTAX: for k = start:step:stop block end start = initial value step = incremental value stop = terminating value See p. 212 for flowchart of for loop. for LOOP FLOW CHART EXAMPLE for k = 5:10:35 x = k^2 end for … end Loops (p. 211) for k = 5:10:35 x = k^2 end Means: starting with k = 5, execute the statements between for … end; then increment k by 10 and execute the statements with k = 15; etc. until k 35. Then exit the loop (k=? at this point) for … end Loops cont’d. Step value may be negative (default is positive 1) For step 0, loop does not execute if start stop For step 0, loop does not execute if start stop If start = stop, loop executes once Non-integer step values give unpredictable results (don’t use them!) INDIVIDUAL EXERCISE (5 min.) Evaluate xn = sin (np/10) for n between 1 and 10 (in increments of 1). Write a Matlab PROGRAM. (Plot x versus n) Save file on R:\ and name file after an historical figure. SOLUTION for n = 1:10 x(n) = sin(n*pi/10); end plot(1:10,x) % or plot(x) title(‘In-class… example’) xlabel(‘n’)