Notes

HW_5 Part 2:
MSG---> user
updated key--> made this go through msg. letter by letter
apply math from announcement

HW_6 is different: Code Debugging Homework
Fixing mistakes in code that's already written
**A New Play fair Cipher code with mistakes**

HW6 + HW7 --> matrices
(1D data: vectors and strings)
(2D data: plotting/graphing x vs. y, excel)
(3D data: modelling, solid-works, images (rows vs. color )

Syntax for 2D:
variable = [ values ; values... ];
(where values = numbers or letters--> single quotes needed)
(where the ";" means create new row)

1 2
3 4
5 6
3 x 2 (rows vs. columns 2D matrix)
table = [1 2; 3 4; 5 6] . . .**(all rows must have same length)**
(can use a space or comma to separate values)

How to change / update values in a matrix???
(2 spots)---> what row? what column? (3D matrices---> 3 spots)
variable (row , column) = #

For vectors---> length
For matrices---> size
syntax: [rows, cols] = size(variable); (left hand side must be in brackets to get back both options)

Special Matrix Commands---> :operator
variable( : , # ) ; variable ( #, : );
where "#" means column you want, and ":" means all of
where "#" means row you want, and ":" means all of

Multiply Vectors:
vecotr .* vector ( the dot fixed issues so it mulyiplies element by element

**** GO TO MATLAB COMMAND WINDOW ****
table = [2 5 6 ; 7 8 9 ; -1 4 5]
to change the 8 to 22--->type table(2 , 2) = 22
table (end, end) = 45 to change last row, last column
[rows,cols] = size(table) ---> row = 3, column = 3 or even [ii,jj]

table (: , 3) = table (: , 3)* -1
table (: , 2) = 0
table(3, :) = table(3, :) * [10 20 30]

table = [1 2 3 ; 4 5 6]
table(3 , :) = [7 8 9]

New CODE:
clc; clear;
%given a 2d matrix from the user, delete any rows with a 0
matrix = input('Enter your 2D matrix: ');
%set a for loop up and get size of matrix
[rows,cols] = size(matrix);
for ii = rows:-1:1
for jj = 1:1:cols
if matrix(ii , jj) == 0
matrix (ii , :) = []; <---makes go away
break;
end
end
end
%Display new matrix
disp(matrix)

enter: [5 7 8; 0 1 4; 3 4 5]
**run**
crashes ---> exceeded matrix dimensions
FIX by counting backwards (change 1:1:rows to rows:-1:1)

**MATRIX TIPS**
table = randi (100, 6, 6)
random table #'s 1-100 with 6 rows and 6 columns
table = randi [50 100], 6, 6)---> makes #'s 50-100
table(2 : 5 , 2 : 5)=0 ---> makes rows 2-5 and cols 2-5 all = 0
table(2 : end-1 , 2 : end -1) = 0

**INTRO for Thurs.**
Matlab solves word search puzzles for us