MATLAB FUNDAMENTALS:MATRIX/ARRAY FUNCTIONS THE COLONMATRIX/ARRAY MANIPULATIONINPUT/OUTPUT

HP 100 – MATLABWednesday, 9/3/2014

www.clarkson.edu/class/honorsmatlab

Before We Begin:

Any Questions? Comments? Concerns? Feel free to contact Joe or Jim

We can set up small group tutoring or one-on-one

You can email us with any questions or concerns

We are here for you! Even if it isn't about MATLAB

Quote/Video of the Week

“English is ambiguous. If someone said, ‘The horse flies like the devil,’ they could either be advising me on a horse race, or merely commenting on the rising tide of Satanism among some insects.”

- Professor Felland

Foundations of Mathematics

https://www.youtube.com/watch?v=I15bDqhkxwE

Matrix/Array Functions

A = [1 1 1; 1 1 1]

B = [0 0; 0 0; 0 0]

C = [1 1; 1 1]

A =A = 1 1 11 1 1 1 1 11 1 1

B =B = 0 00 0 0 00 0 0 00 0

C =C = 1 1 1 1 1 1 1 1

Matrix/Array Functions

A = ones(2,3)

B = zeros(3,2)

C = ones(2)

A =A = 1 1 11 1 1 1 1 11 1 1

B =B = 0 00 0 0 00 0 0 00 0

C =C = 1 1 1 1 1 1 1 1

Matrix/Array Functions

Built in Commands/Functions: See Tables 3.5,6,7 max : Maximum Value min : Minimum Value mean : Mean Value median : Median Value sum : Sum of Vector prod : Product of Vector

Matrix/Array Functions

Sorting Functions Table 3.8 sort sortrows

Size Functions Table 3.9 size Dimensions of Array length Largest Dimension

Special Values / Misc.

The following have special meanings: pi - The constant 3.141592 … i,j - Imaginary Number Inf - Infinty, or overflow NaN - Not a number, Undefined (0/0) clock - [year month day hour minute

seconds] date

The Colon Operator

Used for: Creating Vectors Referencing arrays Future applications [loops]

Creating Vectors

A = [2 4 6 8 10 12]

B = [2:2:12]

C = [4:6:30]

A =A = 2 4 6 8 10 122 4 6 8 10 12

B =B = 2 4 6 8 10 122 4 6 8 10 12

C =C = 4 10 16 22 284 10 16 22 28

The Colon Operator

Let:

A(2,3) = A(1, :) = A(:, 3) = A(:, 1:2:4) =

A =A = 2 9 -3 102 9 -3 10 -4 13 1 6 -4 13 1 6

The Colon Operator

Built-in function – end

A(:,end)= [13; 6; 8] A(end,end) = 8 diag(A) = [4; 2; 8]

A =A = 4 4 7 7 1313 5 5 22 66 1 9 1 9 88

Matrix/Array Manipulation

You can define new arrays or matrices in terms of other arrays or matrices. This can be tricky, but always try to say it

out loud and visualize what is happening.

I/O – Input / Output

Definition: Hardcoding: Setting variables equal to

particular numbers in the code. Example:

Calculate the square root of a number. number = 100; sqrt_of_number = sqrt(number);

The code snippet always calculates the square root of 100, unless you manually change the code.

What if we want to do it for the number the user chooses (whomever is using your program/code)?

I/O – Input / Output

Methods: Ask the user for input through the

command window. Load data from files. Function inputs (We will get to this in a few weeks.)

Input Command: number = input('Please Specify a Number: ');

I/O – Input / Output

Loading data from files: Many different ways, depending on what

type of file it is. We do this in the future. Use the load command.

I/O – Input / Output

Calculations, Manipulation, Calculations… We Still need to display our Results

Methods: Display in the command window

Good for quick solutions, small amount of data. Commands: disp fprintf

Write the results to a file. Great for processing and saving lots of

information. A bit harder to do, can be highly customized. Commands: fprintf save

I/O – Input / Output

Command: disp Example:

x = 5; disp(x); disp(['The value of x is ' num2str(x) ‘. Cool Ehh?’]);

Tells MATLAB to combine everything inside together into an array, in this case, a character array

Things inside of single quotation marks are strings, or just simply text (stored as plain text)

Converts a number to a string.

I/O – Input / Output

Command: fprintf This can be used to either print out to the

command window or write to a file. This is saved for your own reading/learning. It’s another way to display, also. It allows

for more formatting and pretty outputs

Example Code Time

The Golf Ball Example Please take note of lots of little things that

are done, they add to the readability and to the end results being pretty

Problem Description: Calculate the X-Position and Y-Position of a golf

ball hit with an initial speed and angle. Assume constant acceleration from gravity and no drag. Also find the maximum height and display the results.

Homework

Please review/read: Chapter 3, Chapter 4 It is very important to review the tables

indicated and go through the example problems.

Please do: 3.4, 4.1, 4.6

Before you go…

Do Problem 4.1 in the book