1. Week 4 - Wednesday
CS 113

2. Last time What did we talk about last time? Data storage Databases
Shapes in Visual Python

3. Project 1

4. Questions?

5. Data Mining

6. Data mining
Data mining means looking for patterns in massive amounts of data
These days, governments and companies collect huge amounts of data
No human being could sift through it all
We have to write computer programs to analyze it
It is sort of a buzzword, and people argue about whether some of these activities should simply be called data analysis or analytics

7. What can you do with it?
It is a form of machine learning or artificial intelligence
At the most general, you can:
Cluster analysis: Find a group of records that are probably related
Like using cell phone records to find a group of drug dealers
Anomaly detection: Find an unusual record
Maybe someone who fits the profile of a serial killer
Association rule mining: Find dependencies
If people buy gin, they are also likely to buy tonic

8. Businesses love data mining
Seeing patterns in the warehouses can help improve their inventory management
Seeing patterns in sales can help them prepare for changing demands from customers
The items a customer buys can prompt them to rearrange the store to encourage other purchases
People make 20 million trips to Walmart each day
Lots of data to analyze
Given information about potential customers, businesses can contact those that are most likely to be interested

9. Data mining in action
What do Walmart, hurricanes, and Pop-Tarts have to do with one another?
A 2004 NY Times article says that Walmart's analysis shows the demand for strawberry Pop-Tarts goes up by a factor of 7 before a hurricane makes landfall
But the top selling item is beer

10. Privacy Social media providers have access to lots of data
Facebook alone has details about over a billion people
Can they find hidden patterns about your life?
Should they inform the police if they think they can reliably predict crime?
What about data the government has?
For research purposes, some sets of "anonymized" data are made public
But researchers often discover that the people involved can be discovered anyway

11. But back to beer…
Walmart did some data mining and discovered that, on Friday afternoons, young American males who buy diapers are more likely to buy beer
It's an appealing story because the result isn't expected
But it's also not true:
Walmart may have done analysis along those lines, but no story was published
Its roots go back to a story in 1992 when Osco Drugs did analysis that showed that all customers who shopped from 5-7pm were more likely to buy diapers and beer
Even if it were true, data mining is statistical in nature
Correlation is not causation

12. Data mining in science
Looking for patterns in DNA can help find links between genetics and diseases like cancer
Data mining can find trends in negative reactions to prescription drugs
It has even been applied to college education to see why some students learn better than others (and even why some drop out)

13. And beer yet again…
The free Internet dating website okcupid.com was built by people who wanted to use good computer science to match people
They stopped updating their blog (blog.okcupid.com) in 2011, but they published some interesting analysis:
If you want to know if someone will have sex on their first date, ask:
Do you like the taste of beer?
If you want to know their politics, ask:
Do you prefer life to be simple or complex?
If you want to know if they are religious, ask:
Do spelling and grammar mistakes annoy you?
You can read more at your own risk, noting that the subject matter is mature

14. Python Loops

15. Loops
If you want to do something repeatedly, you will use a loop in most languages
The loops in Scratch were
The repeat loop which runs a fixed number of times
The forever if loop which runs forever if a condition is true
The forever loop which runs forever
The repeat until loop which runs until a condition becomes true
We only used the forever loop and the repeat loop

16. Loops in Python Good news: There are only two loops to learn in Python
The while loop runs as long as a condition is true
In this case, when countdown becomes 0, the loop stops (since 0 is not less than 0)
countdown = 10
while countdown > 0:
print(countdown)
countdown = countdown – 1
print("Blast-off!")

17. For loop
Perhaps the most common loop in Python is the for loop, which will loop over everything in a list of things
This code prints each letter in the text on a separate line
for letter in "Help me!":
print(letter)

18. Repeating a set number of times
If you want to do something, say, 10 times in Python, you can use a for loop
But you need to call the range() method to generate a list of numbers for you
In this case, the loop will run 10 times, and the numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 will print out
for i in range(10):
print(i)

19. Annoying syntax colon tab
The first line of every loop ends with a colon (:)
If you don't put it there, Python will not run your code
The stuff inside of a loop needs to be indented with a tab
That's how you know what should be repeated and what is after the loop
If you type the colon, most Python editors automatically indent the next line for you
colon
for i in range(10):
print(i)
tab

20. For loop example
What if we wanted to display 10 red balls on the Visual Python screen?
Each time the loop runs, a ball is created
If they were all in the same position, we would only see one
To fix that problem, we start with x at -5 and increase it by 1 every time
x = -5
for column in range(10): sphere(pos=vector(x,0,0),radius=.25,color=color.red)
x = x + 1

21. Loops inside of loops We can repeat while repeating something else
What if we wanted to display 4 rows of 10 red balls on the Visual Python screen?
The inner loop is like the previous slide, but we run it inside of an outer loop
We had to add a y variable so that each row is on a different line
y = -2
for row in range(4):
x = -5
for column in range(10):
sphere(pos=vector(x,y,0),radius=.25, color=color.red)
x = x + 1
y = y + 1

22. Random numbers value = random() value = (b – a)*random() + a
In Scratch there was a green block that allowed us to create random numbers
In Python, there are functions that give us random values
Unfortunately, GlowScript only supports one of these methods, random(), which gives a random floating point value between 0 and 1
If you want a value between a and b, you can do the following:
These are always floating point values, but you can use the int() conversation operator to make integers
value = random()
value = (b – a)*random() + a
value = int((b – a)*random() + a)

23. Random color for a sphere
Recall that we represent color as a group of red, green, and blue intensities
In Visual Python, those intensities are between 0 and 1
We can create a sphere with a random color as follows
color1 = vector(1.0, 0, 0) #bright red
color2 = vector(1.0, 1.0, 1.0) #white
color3 = vector(0, 0, 0) #black
red = random()
green = random()
blue = random()
sphere(pos=vector(0,0,0), radius=1, color=vector(red, green, blue))

24. Quiz

25. Upcoming

26. Next time…
Review
Lab 4

27. Reminders Finish Project 1 Review Python Chapters 1 – 3
Due this Friday before midnight
Review Python Chapters 1 – 3
Review Blown to Bits Chapter 1
Study for Exam 1 next Monday