% ECE 1250 Lecture 4

Draw lines showing connecting the operator to the description:  pp. 2-12 to 2-13
.*    Addition (+)
 ^    Subtraction (-)
 /    Multiplication (*)
 '    Division (/)
 \    Left division (\)
 +    Power (^)
 *    Complex conjugate transpose (')
()    Element-by-element multiply (.*)
.'    Element-by-element division (./)
./    Transpose (.')
 -    Specify order of evaluation ( () )

%-------------------------------------------------------------------------------
% Eye function.  Matlab¨ Primer pp. 3-9
%-------------------------------------------------------------------------------
>> Ident_mat = eye(3)   % Create identity matrix.
Ident_mat =
     1     0     0
     0     1     0
     0     0     1

% Functions like eye, rand, ones, etc. allow for creation of a square matrix
%  when only one argument is used, or a specified number of rows and cols if
%  two arguments are used.
>> eye(2,3)
ans =
     1     0     0
     0     1     0

%-------------------------------------------------------------------------------
% Functions with multiple return values, such as min and max p. 1-17 and size.
%-------------------------------------------------------------------------------
>> A = magic(3)
A =
     8     1     6
     3     5     7
     4     9     2

>> [max_val, index_of_max] = max(A)    % finds max of cols
max_val =
     8     9     7
index_of_max =
     1     3     2
% We choose the names of the returned variables such as max_val and index_of_max





%-------------------------------------------------------------------------------
% Size command p. 1-11, 2-29, length command p. 2-36.
%-------------------------------------------------------------------------------
>> B = [1, 2]
B =
     1     2

% The size function allows us to find out how big B is.
>> [n_rows, n_cols] = size(B)
nrows =
     1
ncols =
     2

% The size command may be used with two arguments to find out just one
%  dimension at a time.
nrows = size(B,1)   % The 1 means dimension 1, which is rows
ncols = size(B,2)   % The 2 means dimension 2, which is cols

% The length command tells us the largest dimension of an array.
>> B = ones(2,5);
>> length(B)
ans =
     5

>> B = ones(4,3);
>> length(B)
ans =
     4

% Length is especially useful for vectors (arrays with one row or col),
%  since you don't have to know whether the vector is horizontal or vertical.

%-------------------------------------------------------------------------------
% character strings pp. 1-15 to 1-16
%-------------------------------------------------------------------------------
% We can create character variables.
a = 'Hi'

% Need an apostrophe inside the string?  Use two apostrophes in a row.
b = 'Let''s do this!'  % How does Matlab know we are not done with the string
                       %  after the first ' ?  Answer: it sees another ' .
                       % If there is an odd number of ' you are in the string.

>> n = str2num('15')     % Convert a string into a number.
n =
     15

>> n = num2str(15)    % Convert number into string.
n =
15

% We can concatenate strings.  Strings are just arrays.
long_str = ['There are ', num2str(n), ' students in the lab']
% Be careful to put spaces in the string.


% A simple command for displaying strings:
>> display('long_str')

% If you want an apostrophe in a string, use two apostrophes.
>> display('That''s a magic square!')
That's a magic square!

%-------------------------------------------------------------------------------
% Advanced Indexing.  Continue from previous point in handout.
%  (See handout on website.)
%-------------------------------------------------------------------------------