E7 Midterm Exam 1. #11: TuTh 8-10 #12: TuTh #13: TuTh 12-2 #14: TuTh 2-4 #15: TuTh 4-6 #16: MW 8-10 #17: MW #18: MW 2-4 #19: MW 4-6

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1 Exam Date: October 10 E7 Midterm 1, Fall 2014 E7 Midterm Exam 1 NAME : SID : SECTION : 1 or 2 (please circle your discussion section ) LAB : #11: TuTh 8-10 #12: TuTh #13: TuTh 12-2 #14: TuTh 2-4 #15: TuTh 4-6 #16: MW 8-10 #17: MW #18: MW 2-4 #19: MW 4-6 Problem Points Points TOTAL 56 Carefully read and follow these instructions: 1. Write your name on the top left corner of each page. 2. Start answering the exam only when instructed to do so. 3. Record your answers only in the spaces provided. 4. You may not ask questions during the exam. 5. You may not leave the exam room before the exam ends. 6. You may not use any electronic devices. 7. You may use one sheet (2 pages) of handwritten notes. 8. Count the number of pages before the start of the exam. There should be 10 pages. 1 of 10

2 1. Matlab Workspace (a) Referring to the screenshot below, What is the value of ans after executing this line of code? (b) If whos is entered on the next line in the command window, what output information is expected (provide at least 3 items discussed in class)? 2 of 10

3 2. Matlab as a Calculator For each of the following expressions, write what MATLAB would display if the expression were executed in the MATLAB command window. Exact formatting is not important. If the expression contains a syntax error, write error. If MATLAB would not display anything (besides the text itself typed in), write blank. (a) >> a = 4; b = 2ˆ4; c = b/a; c (b) >> a = 4; b = 2ˆ(5); c = b/a; c (c) >> 1ˆ2ˆ4; (d) >> sqrt(4 + 5) (e) >> ln(1) (f) >> i = 3; y = 10; a = i/y; clear i; [a i] (g) >> log(exp(1)) 3 of 10

4 3. Logical operators Define: A = [1, 0, 0]; B = [1, 1, 0]; Write the expected Matlab output. Show your work. (a) >> A & B (b) >> A && B (c) >> A B (d) >> sum(a) min(sqrt(a.ˆ3+3*b.ˆ2)) (e) >> any(a) && all( A + B) 4 of 10

5 4. 1D and 2D Arrays (a) Z = Write the code to create the above array as a concatenation of four column arrays, and assign the value to the variable name Z. (b) Y = [ Write the code to create the above array, Y, in one line using one call the array Z. ] (c) Y = Using the arrays Y and Z, create the above array X. [ ] (d) What is the output of A after executing the code block below? >> A = [1 4; 2 9; 3 7]; >> B = [3 5; 6 0; 4 0]; >> A(B>=4) = 3; 5 of 10

6 5. If-else-end and Switch-case Given the following code for a switch-case condition, re-write the code using an if-end statement (fill in the blanks below). begin code 1 team = 4; 2 3 switch team 4 case {2,4,8} 5 disp('power of 2'); 6 case {3,9,27} 7 disp('power of 3'); 8 case {5,25,125} 9 disp('power of 5'); 10 otherwise 11 disp('cannot compute!'); 12 end 1 team = 4; end code begin code 2 if 3 disp('power of 2'); 4 elseif 5 disp('power of 3'); 6 elseif 7 disp('power of 5'); 8 else 9 % Output a line that states "I don't know!" 10 disp( ); 11 end 12 end code 6 of 10

7 6. Loops Fill in the blanks for the output by Matlab in the command window: 1 >> clear all 2 >> sum = 0; 3 >> for i =1:4 4 sum = sum+i^2; 5 end 6 >> sum 7 sum = >> sum = ones(2,2); 12 >> count = 0; 13 >> for k=1:2 14 for j = 1:2 15 sum(k,j) = sum(k,j)+i^2; 16 count = count + k*j; 17 end 18 end 19 >> sum 20 sum = >> k 24 k = 25 begin code >> count 28 count = 29 end code 7 of 10

8 7. Read the following code, then answer the following questions. 1 StepSizes = [0.5, 1, 1.5]; 2 k = 0; 3 i = 1; 4 StepCount = 0; 5 Distance = 0; 6 Goal = 10; 7 8 while Distance < Goal 9 if i <=3 begin code 10 OneStepSize = StepSizes(i) + sum(stepsizes)/numel(stepsizes) 11 Distance = Distance + OneStepSize; 12 StepCount = StepCount + 1; 13 k = k+1; 14 i = i+1; 15 else 16 i = 1; 17 end 18 end end code (a) What is the value of sum(stepsizes)/numel(stepsizes)? (b) What are the possible values for OneStepSize (c) After the script has finished running, what is the value of the variable Distance? (d) After the script has finished running, what is the value of the variable StepCount? (e) True or false: After the script has finished running: k == StepCount 8 of 10

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10 8. An E7 student writes the following function to calculate the volume of a cylinder. It turns out that this code produces an error when one runs vol = cylinder volume(1, 10) on MATLAB. 1 function V = cylinder_volume(radius,height) 2 V = A*height; 3 end begin code 4 5 function A = circle_area(radius) 6 A = pi*radius^2 7 end end code (a) Point out which line number in the function that is problematic, and explain why. (b) Fix the function by rewriting the particular line that causes the problem (you can only write one line of code). (c) Change the function circle area to output a function handle, h, to the main function. (d) The E7 student wants to calculate the volume of the above cylinder using the following line of code: vol = cylinder volume(1, 10). Will the above code properly calculate the volume for the above shape? What values will be returned to the comand window? 10 of 10