Rating a Shoe

Objectives:1. Explain how sequence, selection, and

iteration are building blocks of algorithms2. Create equations with two or more

variables to represent relationships among quantities.

Warm-Up

R = 3L + 3P + 2C + 2F1. Solve for R given the following variable values:

a) L = 7 P = 4 C = 8 F = 6b) L = 9 P = 8 C = 7 F = 4

2. Describe the relationship between variables L, P, C, & F.c) Do they all affect R equally?d) How does L affect R? e) How does L’s effect on R compare to P’s? f) How does L’s effect on R compare to C’s?

Factors for Choosing Shoes

Discuss with your neighbors: What factors go into choosing a shoe?

Factors for Choosing Shoes

Looks, Price, Comfort, Function

Which Shoe is Better?

Shoe 1

Price: $180Comfort: pretty good, a little stiff, not that cushionyLooks: multiple colors, fancy style, famous brandFunction: medium weight, very durable, supportive

Shoe 2

Price: $45Comfort: okay, loose fit, not much cushionLooks: classic, retro, many color choices, minimal styling, famous brand

Function: medium weight, low durability, little support

Shoe 3

Price: $160Comfort: very good, soft, warm Looks: simple, one color, minimal stylingFunction: light weight, not durable, little support

Computing a Problem

1. Identify Factors: Variables

2. Quantify: Numbers & Units

3. Express the Relationship: Equation

4. Algorithm: How my mind does it

5. Coded Algorithm: How computer does it

Which Shoe is Better?

Shoe 1

Price: $180Comfort: pretty good, a little stiff, not that cushionyLooks: multiple colors, fancy style, famous brandFunction: medium weight, very durable, supportive

Shoe 2

Price: $45Comfort: okay, loose fit, not much cushionLooks: classic, retro, many color choices, minimal styling, famous brand

Function: medium weight, low durability, little support

Shoe 3

Price: $160Comfort: very good, soft, warm Looks: simple, one color, minimal stylingFunction: light weight, not durable, little support

How do we compute a rating (0 to 100) for

each shoe?

Which Shoe is Better?

Shoe 1

Price: $180Comfort: pretty good, a little stiff, not that cushionyLooks: multiple colors, fancy style, famous brandFunction: medium weight, very durable, supportive

Shoe 2

Price: $45Comfort: okay, loose fit, not much cushionLooks: classic, retro, many color choices, minimal styling, famous brand

Function: medium weight, low durability, little support

Shoe 3

Price: $160Comfort: very good, soft, warm Looks: simple, one color, minimal stylingFunction: light weight, not durable, little support

We need numbers!

We need to Quantify it!

Shoe 1

Price: $180Comfort: 6Looks: 8Function: 8

Shoe 2

Price: $45Comfort: okay, loose fit, not much cushionLooks: classic, retro, many color choices, very minimal styling, famous brand

Function: medium weight, low durability, not supportive

Shoe 3

Price: $160Comfort: very good, soft, warm Looks: classic, retro, two colors, minimal styling, famous brandFunction: light weight, kinda durable

Rate the factors on a scale from 0-10.

0 = worst 10 = best

We need to Quantify it!

Shoe 1

Price: $180Comfort: 6Looks: 8Function: 8

Shoe 2

Price: $50Comfort: 5Looks: 7

Function: 6

Shoe 3

Price: $120Comfort: 8Looks: 7Function: 6

But what about the price? It isn’t in the same units as

the others.

We need to Quantify it!

Shoe 1

Price: $180 (1)Comfort: 6Looks: 8Function: 8

Shoe 2

Price: $50Comfort: 5Looks: 7

Function: 6

Shoe 3

Price: $120Comfort: 8Looks: 7Function: 6

We need to rate the price using the same scale (0 to 10) .

0 = Expensive, 10 = Inexpensive

Selection

If price <= 20 Then price = 10ElseIf price <= 40 Then price = 9Etc…

Which Shoe is Better?

Shoe 1

Price: $180Comfort: pretty good, a little stiff, not that cushiony

Looks: multiple colors, fancy style, famous brand

Function: medium weight, very durable, supportive

Shoe 2

Price: $45Comfort: okay, loose fit, not much cushionLooks: classic, retro, many color choices, minimal styling, famous brand

Function: medium weight, low durability, little support

Shoe 3

Price: $160Comfort: very good, soft, warm Looks: simple, one color, minimal stylingFunction: light weight, not durable, little support

Do all the factors have the same importance?(We all know looks matters more than comfort, right?)

Priority

• Put the four factors in order from most to least important.

Price, Comfort, Looks, Function1. _________________ (most important)2. _________________3. _________________4. _________________ (least important)

Weighting the Priorities

• You have a total of 10 weights to use. Allocate the weights based on priority.

1. Looks x 3 2. Price x 33. Comfort x 24. Function x 2

Adds up to 10

____10

Equation to Rate a Shoe

Price: ____

Comfort: ____

Looks: ____

Function: ____

x ____ = ____

x ____ = ____

x ____ = ____

x ____ = ____

+

+

+

Rating: _________

0 to 10 Weight Total

Sample Calculation

Price: 9

Comfort: 6

Looks: 7

Function: 5

x 2 = 18

x 2 = 12

x 4 = 28

x 2 = 10

+

+

+

Rating: 68

0 to 10 Weight Total

Sequence

TextWindow.WriteLine("Rate the price:")price = TextWindow.Read()

VS.

price = TextWindow.Read()TextWindow.WriteLine("Rate the price:")

Selection

If repeat = "y" Then Goto StartEndIf Checks if the user

types in “y”

Iteration

If repeat = "y" Then Goto StartEndIf Checks if the user

types in “y”Goes back to beginning and

repeats program

‘top of program codeStart: GraphicsWindow.Draw...

Exit Card

1. Write down the equation you used to rate a shoe.

2. Write example sets of inputs for two shoes and calculate the rating.

3. Describe the relationship between the input variables.

a) How does each affect the rating? b) Compare one variable’s effect to another.