Notes

MATLAB HW questions:
From Chapter 7:
1,2,7 and 34
From Chapter 8:
1,2,20,21 and 26.

User build functions
Start with an m file that has nothing on it, and it will have to start with the word function
function[output1, output2,....] = name(input1, input2, .....)
code that relates the input to the out put

TO MAKE:
1st line: function[A] = fives(r,c) % defining line of the function to be created
%A is the output of the function
%r is the first input of the function
%c is the second input of the function
%Code:
A= 5*ones(r,c); <--needs to connect your input to your output.
%Command Window
B= fives(2,4)
B =
5 5 5 5 5
5 5 5 5 5
5 5 5 5 5

%new m file to make a general matrix multiplicator
fuction[output] = multiplicator_of_matrix(r,c,n);
% output is the output of the function
%r is the 1st input of the function
%c is the 2nd input if the function
%n is the 3rd input of the function
%Code:
Output = n*one(r,c);
%Command Window:
c= multiplicator_of_matrix(4,5,3)

c =
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3
3 3 3 3 3

New m file:

function[surface,volume] = ball(radius) % defining line of function that takes radius of the ball and calculates SA & V.

%radius is the only input
%surface and volume are outputs

%Code:

fi radius > 0
surface = 4*pi*radius^2;
volume= 4/3*pi*radius^3;
else
surface = 'error';
volume = 'error';
end

%Command Window

[A,B] = ball(3)
A=
113.0973
B=
113.0973

[A,B] = ball(-1)
A=
'error'
B=
'error'

Output = ball(2)
output = 50.2655 % <----in this case because only one variable was declared the program only gave the answer of one of the variable in this case SA.
[Output1, Output2]= ball(2)

Output1=
50.2655
Output2=
33.5103

Matlab Lecture 8 pt. 2

Polynomial a_nX^n +a_n-1 X^n-1 + a_n-2 X^n-2 + ......

p1 = 3
p2 = 2x+1
p3 = x^2 + x + 1

for example x^2 - x +3 is inputed as:
p = [1 -1 3]
and x^2 + 3 is inputed as:
p = [1 0 3] %the zero is there because there is no coefficient that has X^1 in the function therefore the constant for that is 0.

% the 3 function types we will be learning today involve Polyval, roots, and polyfit.

%MATLAB:

clear;clc;

%%%Polyval evaluates the value of a given polynomial for a point or a vector of points.
%%Evaluation of 8x + 1 is written as:

p = [8 1]; %coefficient of the polynomial in order from the highest to the lowest.
x = 0;
a1 = polyval(p,x) %this will evaluate the equation 8x+1 at x=0
a1 =
1
%evaluate -2x^2 + 2x -1
p=[-2 2 -1];
a2 = polyval(p,x)
x = 01:0.01:1
figure(1)
plot(x, x.^2)
figure(2)
plot(x, polyval([1 0 0], x))

%%Evaluate the root of a given polynomial
%%finding the root for
p=[1 -12.2 40,59 -17.015 -71.95 35.88]
ROOTS = roots(p)

%polyfit

ex: p1 = polyfit(x,y,1) <--- (data, data, degree of polynomial you want.