Contents

%%Introductory MATLAB exercises
% A.J. Melhus 3/7/10

% Here are some exercises that are a helpful way of introducing Matlab to the
% first-time student:

2 important areas where first-time users forget/neglect to look:

The directory - this is the current computer directory where Matlab looks
for code/files, should you call upon a created file.  This is especially
important when using m-files for classes/homeworks.
%  The workspace - this area looks very similar to an Excel GUI that many
% people are used to.  The workspace lists the current matrices/vectors/data
% that are stored in Matlab's working memory.  Picking through the workspace
% is sometimes helpful when sorting out plotting problems - "why does my
% plot look like a straight line?"

Creating and using vectors

1) Try typing:

x = [1:50]  % a huge (unnecessary) list of numbers!  (with default step 1)
x =

  Columns 1 through 21 

     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16    17    18    19    20    21

  Columns 22 through 42 

    22    23    24    25    26    27    28    29    30    31    32    33    34    35    36    37    38    39    40    41    42

  Columns 43 through 50 

    43    44    45    46    47    48    49    50

% As you can see, this command generates a huge list of numbers.  Suppress
% command-line echo with the semicolon operator, ;
% Instead, type:
x = [1:50];
% huge list is still there, just supressed.  To check? - open the workspace
% entry for x by typing
x
x =

  Columns 1 through 21 

     1     2     3     4     5     6     7     8     9    10    11    12    13    14    15    16    17    18    19    20    21

  Columns 22 through 42 

    22    23    24    25    26    27    28    29    30    31    32    33    34    35    36    37    38    39    40    41    42

  Columns 43 through 50 

    43    44    45    46    47    48    49    50

%You can manually set the step between values:
x1 = [1:.5:50];
% this generates a row vector 1-50 with spacing 0.5 between each value

% To create a vector with a SET number of entries, uses the <linspace>
% command:
x2 = linspace(1,50,200);
% this creates a vector containing 200 entries, numbering 1 to 50 with equal
% spacing between (linearly spaced entries).


% 2) When performing arithmetic operations with vectors in Matlab, make sure
% to put a period <.> after the vector in question.  Otherwise, you will
% usually get error messages.  The period tells Matlab to perform that
% command at every vector position:

    % y = x^3 +x^2/(x^2 + 1)         NO, wrong format (try cut-and-pasting
    %                                this expression to the command prompt)
      y = x.^3 + (x.^2)./(x.^2 + 1); % YES, correct format
% (note: you do not need to use the period with addition/subtraction)


% 3) Matlab is very good at plotting, but you have to know how to tell it
% what you want.

    x = linspace(0, 2*pi);
    y1 = sin(x);
    y2 = cos(x);
    y3 = (cos(x)).^2;
    clf       % "clear figure"
    hold on   % allows more actions to in the plot/figure window
    plot(x, y1, 'b--')  % this says to plot y1 vs. x using a blue dashed line
    plot(x, y2, 'ro')   % plot with red circles
    plot(x, y3, 'g-') % plot with green straight line
    hold off  % release plot

    % There are many other variations of plot subroutines, just type
    % <help plot>