CE 2 Midterm

Sum of elements

sum_x = sum(x)

Average value

mean_x = mean(x)

Maximum value

max_x = max(x)

Minimum value

min_x = min(x)

 Number of elements

len_x = length(x)

Single Input/Output Function

function [outputNumber] = myFirstFunction(inputNumber) 

What is the correct syntax for defining a function in MATLAB?

function [output1, output2] = functionName(input1, input2)

% Function body

output1 = ...;

output2 = ...;

end

Write a function that takes two inputs and returns division, subtraction, and addition

function [out1, out2, out3] = threeOutputs(in1, in2)
    out1 = in1 / in2;   
    out2 = in1 - in2;     
    out3 = in1 + in2;     
end

What will this function return for different inputs?

function z = functionxyz(x, y)

if x == 0

z = 0;

elseif y == 0

z = 1;

else

z = 2;

end

end

If x = 0: returns 0 (regardless of y)

If x ≠ 0 and y = 0: returns 1

If x ≠ 0 and y ≠ 0: returns 2

Create a function that calculates the area of a rectangle

function area = AreaRECT(l, w)
    area = l * w;
end

Identify the data types in this code:

b = double(a);

row_array = [1,2,2; 3,2,2];

mycharacter = {'a'};

mystring = "myname";

a = 2;

myboolean = true;

double(a) - Double precision number

row_array - 2x3 Matrix/Array

mycharacter - Cell array

mystring - String

a = 2 - Double (default numeric type)

myboolean - Logical/Boolean

How do you calculate the number of seconds in 6.78 days?

day = 24; % hours per day

hr = 60; % minutes per hour

min = 60; % seconds per minute

days = 6.78;

seconds = days*day*hr * min;

Convert 2125 lbf/in² to N/mm² (given: 25.4 mm = 1 in, 4.448 N = 1 lbf)

mm = 25.4;

N = 4.448;

in = 1;

lbf = 1;

result = 2125 (in/mm)^2 (N/lbf);

Write code to perform addition, subtraction, multiplication, and division with a=8, b=5

a = 8; 
b = 5; 

add = a + b;    % 13
sub = a - b;    % 3
mul = a * b;    % 40
dv = a / b;     % 1.6

What are the 4 key rules for writing functions?

1. Function name MUST match filename

2. Never assign values to input variables inside function

3. All outputs must be calculated from inputs

4. End the function with end keyword

How do you call a function that returns three outputs?

[var1, var2, var3] = functionName(input1, input2);

Logic Operators for And, OR, NOT, Equals, Not Equals

&&, I I, ~, ==, ~=

How to call function

[a,b] = myFunc(x,y)

Boolean Variables

1 = true, 0 = false

Script

File containing sequence of commands

Pseudo Code

Outline logic in English before MATLAB code

Write a function that returns:

• 0 if x == 0

• 1 if y == 0

• 2 otherwise

if x == 0
    z = 0;
elseif y == 0
    z = 1;
else
    z = 2;
end

Command Window

The interactive area where you can enter individual commands and see immediate results. Great for testing, but work isn't saved. Users can enter commands and run scripts.

Workspace

A window that lists all the variables currently stored in memory, showing their names, values, and classes (types).

Editor

Where you write and edit Scripts and Functions. This is where your code is saved as a .m file.

Current Folder

Shows the files in the directory you are currently working in. Your functions must be saved here to be called.

Double

The default for numbers (x = 5.5)

Branching (If/Else)

allows the code to choose a path.

Characters

Only letters, numbers, and underscores (_) No spaces, no hyphens, no $ or %

std(x)

Standard Deviation

sqrt(x)

Square root

Row Vector

v = [1, 2, 3] or v = [1 2 3] (commas or spaces)

Column Vector

v = [1; 2; 3] (semicolons)

Matrix

M = [1, 2; 3, 4] (A 2x2 square)

a function that returns a letter grade based on numerical score using elseif

function grade = calculateGrade(score)
    if score >= 90
        grade = 'A';
    elseif score >= 80
        grade = 'B';
    elseif score >= 70
        grade = 'C';
    elseif score >= 60
        grade = 'D';
    else
        grade = 'F';
    end
end

a function that gives advice based on temperature using elseif

function advice = temperatureAdvisory(temp)
    if temp > 100
        advice = 'Extreme heat - stay indoors';
    elseif temp > 80
        advice = 'Hot - stay hydrated';
    elseif temp > 60
        advice = 'Pleasant weather';
    elseif temp > 32
        advice = 'Cool - wear a jacket';
    else
        advice = 'Freezing - stay warm';
    end
end

Write an if statement that checks if a number is between 1 and 10 (inclusive)

if x >= 1 && x <= 10
    disp('x is between 1 and 10');
end

a function that checks if someone is eligible to vote (age ≥ 18 and citizen = true)

function eligible = canVote(age, isCitizen)
    if age >= 18 && isCitizen == true
        eligible = true;
    else
        eligible = false;
    end
end

function that classifies a number as positive, negative, or zero using elseif

function classification = classifyNumber(x)
    if x > 0
        classification = 'Positive';
    elseif x < 0
        classification = 'Negative';
    else
        classification = 'Zero';
    end
end

While-Loop

Loop as long as a condition is true

While Loop Example

n = 1;

nFactorial = 1;

while nFactorial < 1e100 % Conditional Statement

n = n + 1;

nFactorial = nFactorial * n;

end

For Loop

Loop a specific number of times

For Loop Example

for i = 2:3:20 % Loop indexing variable

A(i) = A(i) * x

x = x+1

end

If else example (Size)

if x > 10 % 1st Conditional Statement

disp(“It is size large”)

elseif x >= 5 % 2nd Conditional Statement

disp(“The size is medium”)

else

disp(“The size is small”)

end

Plot(x,y)

will create a line on the figure connecting points, where all of the coordinates come from x and y

xlabel(‘string’) ylabel(‘ string’)

These will label your axes with the string you put in the parentheses 

hold on

Stops your current figure from being overwritten

Will plot new lines and scatter plots in different colors so you can distinguish

them

N=length(array)

for i = 1:N

Will counts through all of the indices in array above from 1 to N

Matrices

Multidimensional arrays, Matrices are the 2-dimensional version of arrays. We store numbers in them

[numRows, numCols] = size(x)

This will tell you how many rows and columns are in any matrix