Practice Midterm 2
               CS 205 - Spring 98


This exam is designed to ask you to work with given functions and
scripts and produce the output that MATLAB would.

You should use MATLAB to practice with these.  The actual scripts
and functions have been placed within your MATLAB path, so you can
easily see their output.

You'll want to experiment with these, because the exam itself will
have modified versions of these ideas.  The focus is on the inputs
and outputs from user-defined M-file functions and how they
interact with M-file scripts.

The MATLAB workspace is very important and on the exam you'll be
asked to give the values that each of the variables contains.

So for problem one, you should be able to draw

1)  Given the files:

script1.m
----------
% m-file script [script1.m] for practice midterm 2/cs205/spr98
%
clear % empty the work space
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%
x = 0:0.1:5;
y = -2:5; 
z = 1:2:10;

% invoke the function, "testit1"
[output,dummy] = testit1 (x,y,z);

output
dummy

fprintf(' leaving script1 - did you get the dimensions and shapes correct?\n\n')

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testit1.m
----------
function [out1,out2] = testit1 (in1, in2, in3)
% m-file function devised for practice midterm 1 in cs 205/spr98
% the file is available from the class home page
%     http://www.stewart.cs.sdsu.edu/cs205/
% and from the individual student's rohan account for this course
% so that you can practice with it to check your understanding of
% communications between MATLAB m-file scripts and m-file functions
%
n1 = length(in1); n2 = length(in2); n3 = length (in3); % ; suppressed output
%
out1 = [n1, n2, n3]; % first output parameter is a matrix of size 1 by 3
out2 = [n1; n2; n3]; % second output parameter is a matrix of size 3 by 1
fprintf ('\n leaving m-file function testit1 \n')

===============================================================
Produce the output produced from 

>> script1

  MATLAB workspace
 -------------------------------------
 |                                   |
 |                                   |
 |  indicate contents of x y z       |
 |                       dummy       |
 |                       output      |
 |                                   |
 -------------------------------------

==============================================================
2) similair to 1) with the following example files

script2.m
---------
% m-file script [script2.m] for practice midterm 1/cs205/spr98
%
clear % emtpy the work space
x = -3:0.1:3;
y = rect(x); % a function to compute the "rectangle function"
plot (x,y), title(' Rectangle Function'), ...
xlabel ('x'), ylabel ('y'), grid
fprintf('\n\n finished with script 2 \n\n')
who

rect.m
------
function r = rect (x)
% RECT   The rectangular function is defined to be 1
%        on [-0.5,0.5] and 0 elsewhere
%
% m-file function [rect.m] devised for practice midterm 1 in cs 205/spr98
% the file is available from the class home page
%     http://www.stewart.cs.sdsu.edu/cs205/
% and from the individual student's rohan account for this course
% so that you can practice with it to check your understanding of
% communications between MATLAB m-file scripts and m-file functions
%
% initialize output matrix to be all zeros, same size as input
r = zeros(size(x)); 
%
set1 = find(abs(x) <= 0.5); % identify component of input vector in [-0.5,0.5]
r(set1) = ones(size(set1)); % for those component in [-0.5,0.5], set value 1

===================================================================
3) similair to 1) and 2) with these files

script3.m
---------
% m-file script [script3.m] for practice midterm 1/cs205/spr98
%
% start with an empty workspace
clear
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% invoke the function, "testit1" with constants as inputs
[output,dummy] = testit1 (1,0,[1,2,3,4]);
output
dummy
fprintf(' what were the dimensions of the constants? \n\n')
who

testit1.m
---------
function [out1,out2] = testit1 (in1, in2, in3)
% m-file function devised for practice midterm 1 in cs 205/spr98
% the file is available from the class home page
%     http://www.stewart.cs.sdsu.edu/cs205/
% and from the individual student's rohan account for this course
% so that you can practice with it to check your understanding of
% communications between MATLAB m-file scripts and m-file functions
%
n1 = length(in1); n2 = length(in2); n3 = length (in3); % ; suppressed output
%
out1 = [n1, n2, n3]; % first output parameter is a matrix of size 1 by 3
out2 = [n1; n2; n3]; % second output parameter is a matrix of size 3 by 1
fprintf ('\n leaving m-file function testit1 \n')

========================================================================
4) as above with the following script

script4.m
---------
% m-file script [script4.m] for practice midterm 1/cs205/spr98
%
clear % empty the workspace
s = 'this is a string';
% invoke the function, "testit1"
[output,dummy] = testit1 (s,' what is the length',0);
output
dummy
s
disp(s)
fprintf(' \n\nfinished script 4 \n')
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