clear

% variables -- no definition just use!
a = 3;
b = 4;

% MATLAB is case sensitive

A = a + b; % addition
B = a - b; % subtraction
C = a * b; % multiplication
D = a / b; % division

E = a ^ b; % power

% whos -- show the variables in the workspace

% omitting the semi column ; shows the value of the expression/variable

clear;

% vectors: matrices with either number of rows or columns is 1

% creating vectors
x = [2 8 9 5] % row vector
y = ones(5,1) % column vector
z = zeros(1,4) % row vector
t = [4;6;9;1;0] % column vector
k = 5:2:10 % start with 5, increment by 2 until 10
m = 3:12; % start with 3, use default increment (1) until 12

% create 20 linearly spaced points between 5 and 15
lin = linspace(5,15,20);

% create 15 logarithmically spaced points between 10^2 and 10^4
log = logspace(2,4,15);

% show sizes
size(k)
[numrows, numcols] = size(m)

%accessing vector elements -- indices start with 1
x(3)
y(4)
t(2:4)
y(1:2:5)

%x(6) % out of bounds --- error
%x(5) % out of bounds --- error

x(6) = 8; % not an error, but slows down the process. Better to use preallocated sizes

x
disp(x) % display

% assignment operator
l = k  %row vector

% transpose operator
l = k' %column vector

clear all % clear all memory
%  matrix

% creating matrix
A = [1 2; 3 4];
B = [1,3,4; 5,8,9];
D = zeros(3,5); % D is a matrix with 3 rows, 5 columns, cells initialized to 0
E = ones(2,7);
C = [
    1 4 5 3
    6 8 9 7
    9 11 2 5];

C
%access element
a = C(2,4);

%re-assign value
C(2,4) = -13;

a
C
size(C)

%C(3,6) -- out of bounds

% assign
C(3, 6) = 22;
disp(C)

% + - *  /  \  ^  '
%    .* ./ .\ .^ .'

x=  [1,2,3]; y=[4,5,6];
x+i*y
(x+i*y)'
(x+i*y).'

% matrix concatenation
Xr = [x y];
Xc = [x; y];


% strings
first = 'John';
last  = 'Coltrane';
name  = [first,' ',last]

save wrkspc
clear
load wrkspc
whos

save somevars Xr Xc name
clear
load somevars
whos