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ec/README.md deleted 100644 → 0
# String Matching Extra Credit
*Due 6/7/19 11:59 PM*
Entity Resolution is the task of disambiguating manifestations of real world entities in various records or mentions by linking and grouping. For example, there could be different ways of addressing the same person in text, different addresses for businesses, or photos of a particular object. In this extra credit assignment, you will link two product catalogs.
## Getting Started
First, pull the most recent changes from the cmsc13600-public repository:
```
$ git pull
```
Then, copy the `ec` folder to your submission repository. Change directories to enter your submission repository. Your code will go into `analzy.py`. You can the files to the repository using `git add`:
```
$ git add analyze.py
$ git commit -m'initialized homework'
```
You will also need to fetch the datasets used in this homework assignment:
```
https://www.dropbox.com/s/vq5dyl5hwfhbw98/Amazon.csv?dl=0
https://www.dropbox.com/s/fbys7cqnbl3ch1s/Amzon_GoogleProducts_perfectMapping.csv?dl=0
https://www.dropbox.com/s/o6rqmscmv38rn1v/GoogleProducts.csv?dl=0
```
Download each of the files and put it into your `ec` folder.
Before we can get started, let us understand the main APIs in this project. We have provided a file named `core.py` for you. This file loads and processes the data that you've just downloaded. For example, you can load the Amazon catalog with the `amazon_catalog()` function. This returns an iterator over data tuples in the Amazon catalog. The fields are id, title, description, mfg (manufacturer), and price if any:
```
>>>for a in amazon_catalog():
... print(a)
... break
{'id': 'b000jz4hqo', 'title': 'clickart 950 000 - premier image pack (dvd-rom)', 'description': '', 'mfg': 'broderbund', 'price': '0'}
```
You can similarly, do the same for the Google catalog:
```
>>>for a in google_catalog():
... print(a)
... break
{'id': 'http://www.google.com/base/feeds/snippets/11125907881740407428', 'title': 'learning quickbooks 2007', 'description': 'learning quickbooks 2007', 'mfg': 'intuit', 'price': '38.99'}
```
A matching is a pairing between id's in the Google catalog and the Amazon catalog that refer to the same product. The ground truth is listed in the file `Amzon_GoogleProducts_perfectMapping.csv`. Your job is to construct a list of pairs (or iterator of pairs) of `(amazon.id, google.id)`. These matchings can be evaluated for accuracy using the `eval_matching` function:
```
>>> my_matching = [('b000jz4hqo', http://www.google.com/base/feeds/snippets/11125907881740407428'),...]
>>> {'false positive': 0.9768566493955095, 'false negative': 0.43351268255188313, 'accuracy': 0.04446992095577143}
```
False positive refers to the false positive rate, false negative refers to the false negative rate, and accuracy refers to the overall accuracy.
## Assignment
Your job is write the `match` function in `analzye.py`. You can run your code by running:
```
python3 analyze.py
```
Running the code will print out a result report as follows:
```
----Accuracy----
{'false positive': 0.690576652601969, 'false negative': 0.4926979246733282, 'accuracy': 0.38439138031450204}
---- Timing ----
114.487954 seconds
```
*For full extra credit, you must write a program that achieves at least 35% accuracy in less than 3 mins on a standard laptop.*
## Submission
After you finish the assignment you can submit your code with:
```
$ git push
```
ec/analyze.py deleted 100644 → 0
from core import *
import datetime
def match():
'''
Match must return a list of tuples of amazon ids and google ids.
For example:
[('b000jz4hqo', http://www.google.com/base/feeds/snippets/11125907881740407428'),....]
'''
#YOUR CODE GOES HERE
return []
#prints out the accuracy
now = datetime.datetime.now()
out = eval_matching(match())
timing = (datetime.datetime.now()-now).total_seconds()
print("----Accuracy----")
print(out)
print("---- Timing ----")
print(timing,"seconds")
\ No newline at end of file
ec/core.py deleted 100644 → 0
'''
The core module sets up the data structures and
and references for this programming assignment.
2010
'''
import platform
import csv
if platform.system() == 'Windows':
print("This assignment will not work on a windows computer")
exit()
#defines an iterator over the google catalog
class Catalog():
def __init__(self, filename):
self.filename = filename
def __iter__(self):
f = open(self.filename, 'r', encoding = "ISO-8859-1")
self.reader = csv.reader(f, delimiter=',', quotechar='"')
next(self.reader)
return self
def __next__(self):
row = next(self.reader)
return {'id': row[0],
'title': row[1],
'description': row[2],
'mfg': row[3],
'price': row[4]
}
def google_catalog():
return Catalog('GoogleProducts.csv')
def amazon_catalog():
return Catalog('Amazon.csv')
def eval_matching(matching):
f = open('Amzon_GoogleProducts_perfectMapping.csv', 'r', encoding = "ISO-8859-1")
reader = csv.reader(f, delimiter=',', quotechar='"')
matches = set()
proposed_matches = set()
tp = set()
fp = set()
fn = set()
tn = set()
for row in reader:
matches.add((row[0],row[1]))
for m in matching:
proposed_matches.add(m)
if m in matches:
tp.add(m)
else:
fp.add(m)
for m in matches:
if m not in proposed_matches:
fn.add(m)
prec = len(tp)/(len(tp) + len(fp))
rec = len(tp)/(len(tp) + len(fn))
return {'false positive': 1-prec,
'false negative': 1-rec,
'accuracy': 2*(prec*rec)/(prec+rec) }
hw0/README.md
# Three-Way Iterator Matching
# Submitting Homework Assignments
This document describes the basic procedure for completing and submitting homework assignments.
*Due 4/19/19 11:59 PM*
## Initial Setup
All of the coding exercises in this class with use Python3 (NOT Python 2!!!). Python 3 is installed on all of the CSIL machines and you can install it on your own computer by downloading it here:
[https://www.python.org/download/releases/3.0/]
In this assignment, you will write a 3-way match operator similar to the 2-way match operator you saw in lecture. Consider the following example where you are given three iterable objects i1,i2,i3:
```
>> i1 = [ 1,7,2,4,6, ... ] # iterable
>> i2 = [ 3,6,7,2,1, ... ] # iterable
>> i3 = [ 10,6,1,2,3, ... ] # iterable
```
On your personal computer, you probably navigate your hard drive by double clicking on icons. While convenient for simple tasks, this approach is limited. For example, imagine that you want to delete all of the music files over 5 MB that you haven't listened to in over a year. This task is very hard to do with the standard double-click interface but is relatively simple using the terminal. All of the instructions in this class will assume access to a terminal interface whether windows, linux, or macos. It is your responsibility to get familiar with using your available terminal.
There is a great tutorial linked here on accessing the Python interpreter from your command line:
[http://www.cs.bu.edu/courses/cs108/guides/runpython.html]
## Git
The purpose of Git is to manage a project, or a set of files, as they change over time. Git stores this information in a data structure called a repository. A git repository contains, among other things, the following: A set of commit objects. A set of references to commit objects, called heads.
Git is installed on all of the CSIL computers, and to install git on your machine follow the instructions here:
[https://git-scm.com/book/en/v2/Getting-Started-Installing-Git]
Every student in the class has a git repository (a place where you can store completed assignments). This git repository can be accessed from:
[https://mit.cs.uchicago.edu/cmsc13600-spr-19/<your cnetid>.git]
You should be able to construct a `ThreeWayMatchOperator` object:
The first thing to do is to open your terminal application, and ``clone`` this repository (NOTE skr is ME, replace it with your CNET id!!!):
```
>> threeWayIter = ThreeWayMatchOperator( (i1,i2,i3) )
$ git clone https://mit.cs.uchicago.edu/cmsc13600-spr-19/skr.git cmsc13600-submit
```
and this operator should iterate over all values that appear in ALL
three iterators. The order is not important
Your username and id is your CNET id and CNET password. This will create a new folder that is empty titled cmsc13600-submit. There is similarly a course repository where all of the homework materials will stored. Youshould clone this repository as well:
```
>> for i in threeWayIter:
... print(i)
[2,2,2]
[1,1,1]
[6,6,6]
$ git clone https://mit.cs.uchicago.edu/skr/cmsc13600-public.git cmsc13600-materials
```
## Getting Started
Acquaint yourselves with the basic homework submission procedures and please ask us if you have any question on Piazza or during office hours BEFORE the deadline. Remember there are no "slip days" in this class, it is your responsibility to know how to complete and submit the homework assignments. We will run a tutorial on how to use git on Thursday 4/11 2-3 (in 223 JCL). A summary is below:
https://mit.cs.uchicago.edu/skr/cmsc13600-public/tree/master/using-git
First, pull the most recent changes from the cmsc13600-public repository:
This will create a new folder titled cmsc13600-materials. This folder will contain your homework assignments. Before you start an assingment you should sync your cloned repository with the online one:
```
$ cd cmsc13600-materials
$ git pull
```
Then, copy the `hw0` folder to your submission repository. Change directories to enter your submission repository. Your code will go into `match.py` this is the only file that you will modify. Finally, add `match.py` using `git add`:
Then, we will tell you which of the pulled materials to copy over to your repository (cmsc13600-submit). Typically, they will be self-contained in a single folder with an obvious title (like hw0).
Try this out on your own! Copy the folder ``using-git`` to your newly cloned submission repository. Enter that repository from the command line and enter the copied ``using-git`` folder. There should be a single file in the folder called ``README.md``. Once you copy over files to your submission repository, you can work on them all you want. Once you are done, you need to add ALL OF THE FILES YOU WISH TO SUBMIT:
```
$ git add match.py
$ git commit -m'initialized homework'
$ git add README.md
```
## Doing the homework
You will have to implement `__next__` and `__iter__` to write a 3-way matching operator. One edge case to watch out for is if any of the iterators is empty. In this case, raise an exception. We have provided a series of basic tests in `test.py`, these tests are incomplete and are not meant to comprehensively grade your assignment.
After you finish the assignment you can submit your code with:
After adding your files, to submit your code you must run:
```
$ git commit -m"My submission"
$ git push
```
We will NOT grade any code that is not added, committed, and pushed to your submission repository. You can confirm your submission by visiting the web interface[https://mit.cs.uchicago.edu/cmsc13600-spr-19/skr]
hw0/match.py deleted 100644 → 0
class ThreeWayMatchOperator:
"""
In this assignment, you will write a 3-way match operator
similar to the 2-way match operator you saw in lecture.
Consider the following example where you are given three
iterators i1,i2,i3:
>> i1 = [ 1,7,2,4,6, ... ] # iterator
>> i2 = [ 3,6,7,2,1, ... ] # iterator
>> i3 = [ 10,6,1,2,3, ... ] # iterator
You can construct a ThreeWayMatchOperator object:
>> threeWayIter = ThreeWayMatchOperator( (i1,i2,i3) )
and this operator should return all values that appear in ALL
three iterators. The order is not important
>> for i in threeWayIter:
... print(i)
1. [2,2,2]
2. [1,1,1]
3. [6,6,6]
Edge cases:
* Return an error if any of the iterators has 0 values
"""
def __init__(self, input):
self.in1, self.in2, self.in3 = input
def __iter__(self):
raise NotImplemented("You must implement an initializer")
def __next__(self):
raise NotImplemented("You must implement a next function")
\ No newline at end of file
hw0/test.py deleted 100644 → 0
from match import ThreeWayMatchOperator
def tryOrAssert(fn, output, error=False):
try:
return (fn() == output)
except:
return error
def test1():
r1 = range(0,10)
r2 = range(0,10,3)
r3 = range(0,10,2)
t = ThreeWayMatchOperator((r1,r2,r3))
values = set([v[0] for v in t])
return values
def test2():
r1 = range(0,12)
r2 = range(0,10,3)
r3 = range(0,10,2)
t = ThreeWayMatchOperator((r1,r2,r3))
values = set([v[0] for v in t])
return values
def test3():
r1 = range(0)
r2 = range(0)
r3 = range(0)
t = ThreeWayMatchOperator((r1,r2,r3))
values = set([v[0] for v in t])
return values
def test4():
r1 = range(0,1)
r2 = range(0,1)
r3 = range(0,1)
t = ThreeWayMatchOperator((r1,r2,r3))
values = set([v[0] for v in t])
return values
def test5():
r1 = ['a', 'b', 'c','d']
r2 = ['3', '2', '1','d']
r3 = ['p', 'q', 'a','d']
t = ThreeWayMatchOperator((r1,r2,r3))
values = set([v[0] for v in t])
return values
print("Basic 1", tryOrAssert(test1, {0, 6}))
print("Basic 2", tryOrAssert(test2, {0, 6}))
print("Basic 3", tryOrAssert(test5, {'d'}))
print("Empty",tryOrAssert(test3, None, True))
print("Singleton", tryOrAssert(test4, {0}))
hw1/README.md deleted 100644 → 0
# Out-of-Core Group By Aggregate
*Due 4/29/19 11:59 PM*
In this assignment, you will implement an out-of-core
version of the group by aggregate (aggregation by key)
seen in lecture. You will have a set memory limit and
you will have to count the number of times a string shows
up in an iterator. Your program should work for any limit
> 20.
## Getting Started
First, pull the most recent changes from the cmsc13600-public repository:
```
$ git pull
```
Then, copy the `hw1` folder to your submission repository. Change directories to enter your submission repository. Your code will go into `countD.py` this is the only file that you will modify. Finally, add `countD.py` using `git add`:
```
$ git add countD.py
$ git commit -m'initialized homework'
```
Now, you will need to fetch the data used in this assignment. Download title.csv put it in the hw1 folder:
https://www.dropbox.com/s/zl7yt8cl0lvajxg/title.csv?dl=0
DO NOT ADD title.csv to the git repo! After downloading the
dataset, there is a python module provided for you called `core.py`, which reads the dataset. This module loads the data in as
an iterator in two functions `imdb_years()` and `imdb_title_words()`:
```
>> for i in imdb_years():
... print(i)
1992
1986
<so on>
```
Play around with both `imdb_years()` and `imdb_title_words()` to get a feel for how the data works.
## MemoryLimitedHashMap
In this project, the main data structure is the `MemoryLimitedHashMap`. This is a hash map that has an explicit limit on the number of keys it can store. To create one of these data structure, you can import it from core module:
```
from core import *
#create a memory limited hash map
m = MemoryLimitedHashMap()
```
To find out what the limit of this hash map is, you can:
```
print("The max size of m is: ", m.limit)
```
The data structure can be constructed with an explicit limit (the default is 1000), e.g., `MemoryLimitedHashMap(limit=10)`.
Adding data to this hash map is like you've probably seen before in a data structure class. There is a `put` function that takes in a key and assigns that key a value:
```
# put some keys
m.put('a', 1)
m.put('b', 45)
print("The size of m is: ", m.size())
```
You can fetch the data using the `get` function and `keys` function:
```
# get keys
for k in m.keys():
print("The value at key=", k, 'is', m.get(k))
# You can test to see if a key exists
print('Does m contain a?', m.contains('a'))
print('Does m contain c?', m.contains('c'))
```
When a key does not exist in the data structure the `get` function will raise an error:
```
#This gives an error:
m.get('c')
```
Similarly, if you assign too many unique keys (more than the limit) you will get an error:
```
for i in range(0,1001):
m.put(str(i), i)
```
The `MemoryLimitedHashMap` allows you to manage this limited storage with a `flush` function that allows you to persist a key and its assignment to disk. When you flush a key it removes it from the data structure and decrements the limit. Flush takes a key as a parameter.
```
m.flushKey('a')
print("The size of m is: ", m.size())
```
Note that the disk is not intelligent! If you flush a key multiple times it simply appends the flushed value to a file on disk:
```
m.flushKey('a')
<some work...>
m.flushKey('a')
```
Once a key has been flushed it can be read back using the `load` function (which takes a key as a parameter). This loads back *all* of the flushed values:
```
#You can also load values from disk
for k,v in m.load('a'):
print(k,v)
```
If you try to load a key that has not been flushed, you will get an error:
```
#Error!!
for k,v in m.load('d'):
print(k,v)
```
If you want multiple flushes of the same key to be differentiated, you can set a *subkey*:
```
#first flush
m.flushKey('a', '0')
<some work...>
#second flush
m.flushKey('a', '1')
```
The `load` function allows you to selectively pull
certain subkeys:
```
# pull only the first flush
m.load('a', '0')
```
We can similarly iterate over all of the flushed data (which optionally takes a subkey as well!):
```
for k,v in m.loadAll():
print(k,v)
```
There is also a way to iterate over all of the flushed keys (will strip out subkeys):
```
m.fKeys()
```
## Count Per Group
In this assignment, you will implement an out-of-core count operator which for all distinct strings in an iterator returns
the number of times it appears (in no particular order).
For example,
```
In: "the", "cow", "jumped", "over", "the", "moon"
Out: ("the",2), ("cow",1), ("jumped",1), ("over",1), ("moon",1)
```
Or,
```
In: "a", "b", "b", "a", "c"
Out: ("c",1),("b",2), ("a", 2)
```
The catch is that you CANNOT use a list, dictionary, or set from
Python. We provide a general purpose data structure called a MemoryLimitedHashMap (see ooc.py). You must maintain the iterator
state using this data structure.
The class that you will implement is called Count (in countD.py).
The constructor is written for you, and ittakes in an input iterator and a MemoryLimitedHashMap. You will use these objects
in your implementation. You will have to implement `__next__` and `__iter__`. Any solution using a list, dictionary, or set inside `Count` will recieve 0 points.
The hint is to do this in multiple passes and use a subkey to track keys flushed between different passes.
## Testing and Submission
We have provided a series of basic tests in `test.py`, these tests are incomplete and are not meant to comprehensively grade your assignment. There is a file `years.json` with an expected output. After you finish the assignment you can submit your code with:
```
$ git push
```
hw1/core.py deleted 100644 → 0
'''
The core module sets up the data structures and
and references for this programming assignment.
'''
import platform
import os
import json
if platform.system() == 'Windows':
print("This assignment will not work on a windows computer")
exit()
def imdb_title_words():
f = open('title.csv','r')
line = f.readline()
while line != "":
words = line.strip().split(',')[1].split()
for w in words:
yield w
line = f.readline()
f.close()
def imdb_years():
f = open('title.csv','r')
line = f.readline()
while line != "":
csvsplit = line.strip().split(',')
year = csvsplit[len(csvsplit) - 8]
if year.strip() != "":
yield year
line = f.readline()
f.close()
hw1/countD.py deleted 100644 → 0
"""
Get the dataset first, download title.csv put it in the pa1 folder
https://www.dropbox.com/s/zl7yt8cl0lvajxg/title.csv?dl=0
Count the number of times each symbol shows up in an iterator
with limited memory. Your program should work for any limit
> 20.
"""
class Count:
"""
In this assignment, you will implement an out-of-core count
operator which for all distinct strings in an iterator returns
the number of times it appears (in no particular order).
For example,
In: "the", "cow", "jumped", "over", "the", "moon"
Out: ("the",2), ("cow",1), ("jumped",1), ("over",1), ("moon",1)
Or,
In: "a", "b", "b", "a", "c"
Out: ("c",1),("b",2), ("a", 2)
The catch is that you CANNOT use a list, dictionary, or set from
python. We provide a general purpose data structure called a
MemoryLimitedHashMap (see ooc.py). You must maintain the iterator
state using this data structure.
"""
def __init__(self, input, memory_limit_hashmap):
'''
The constructor takes in an input iterator and
a MemoryLimitedHashMap. You will use these objects
in your implementation.
'''
self.in1 = input
self.hashmap = memory_limit_hashmap
def __iter__(self):
raise NotImplemented("You must implement an initializer")
def __next__(self):
raise NotImplemented("You must implement a next function")
hw1/ooc.py deleted 100644 → 0
import os
import json
class MemoryLimitedHashMap(object):
'''
A MemoryLimitedHashMap simulates a hardware memory limit for a
key-value data structure. It will raise an exception if the
limit is exceeded.
Keys must be strings
'''
def __init__(self, diskfile='disk.file', limit=1000):
'''
The constructor takes a reference to a persistent file
and a memory limit.
'''
if os.path.exists(diskfile):
print("[Warning] Overwriting the Disk File", diskfile)
import shutil
shutil.rmtree(diskfile)
os.mkdir(diskfile)
self.diskfile = diskfile
self._data = {}
self.limit = limit
def size(self):
return len(self._data)
def put(self, k, v):
'''
Basically works like dict put
'''
if not self.contains(k) and len(self._data) == self.limit:
raise ValueError("[Error] Attempting to Insert Into a Full Map: " + str((k,v)))
else:
self._data[k] = v
def get(self, k):
'''
Basically works like dict get
'''
return self._data[k]
def contains(self, k):
'''
Basically works like hash map contains
'''
return (k in self._data)
def keys(self):
'''
Returns a set of keys. Tuple
is (key, location)
'''
return set([k for k in self._data])
def fKeys(self):
'''
Returns a set over keys that have been flushed.
Tuple is (key, location)
'''
return set([self.path2Key(k) for k in os.listdir(self.diskfile)])
def keyPath(self, k, subkey):
return self.diskfile+"/"+str(k)+ "_" + subkey
def path2Key(self, k):
key = k.split("_")[0]
return key
def flushKey(self, k, subkey):
'''
Removes the key from the dictionary and
persists it to disk.
'''
if not self.contains(k):
raise ValueError("[Error] Map Does Not Contain " + k)
f = open(self.keyPath(k, subkey), 'a')
f.write(json.dumps(self.get(k)) + "\n")
f.close()
del self._data[k] #free up the space
def load(self, k, subkey=""):
'''
Streams all of the data from a persisted key
'''
fname = self.keyPath(k, subkey)
if not os.path.exists(fname):
raise ValueError("[Error] Disk Does Not Contain " + k)
f = open(fname, 'r')
line = f.readline()
while line != "":
yield (k, json.loads(line.strip()))
line = f.readline()
def loadAll(self, subkey=""):
'''
Streams all of the data from all keys
'''
for k in self.keys():
yield (k, self.get(k))
for k in self.fKeys():
for _,v in self.load(k, subkey):
yield (k,v)
\ No newline at end of file
hw1/test.py deleted 100644 → 0
from countD import *
from core import *
from ooc import *
import json
test_file = open('years.json','r')
expected = json.loads(test_file.read())
for l in range(80, 140, 20):
m = MemoryLimitedHashMap(limit = l)
actual = {k:v for k,v in Count(imdb_years(), m)}
print("Memory Limit", l, expected == actual)
hw1/years.json deleted 100644 → 0
{"1944": 1831, "1917": 4514, "1907": 1487, "1975": 14054, "1880": 1, "2003": 67777, "2012": 164307, "1958": 9768, "1894": 93, "1904": 1136, "1979": 14926, "1915": 7670, "2010": 141703, "2017": 3, "1982": 14770, "1954": 7199, "2014": 3077, "1948": 2840, "1893": 2, "1923": 2614, "2005": 95005, "2009": 128696, "1992": 24917, "1949": 3847, "1945": 1730, "1896": 791, "1902": 1799, "1976": 13994, "1965": 13063, "1961": 11073, "1951": 5663, "1962": 10308, "1929": 2800, "2000": 53013, "1910": 4597, "1912": 7770, "1898": 1740, "1901": 1747, "1922": 3066, "1957": 9491, "1927": 2915, "2001": 58590, "1940": 2202, "2002": 62568, "1995": 36437, "1913": 8902, "1999": 50564, "1994": 30027, "1932": 2567, "1980": 14779, "1925": 2786, "1983": 15489, "1889": 2, "1973": 14284, "1936": 2798, "1892": 9, "1939": 2483, "1971": 14442, "1981": 14456, "2013": 63827, "1942": 2181, "1968": 14235, "1930": 2543, "1990": 23040, "2015": 401, "1914": 8125, "1909": 3417, "1906": 1104, "1920": 4012, "1972": 13623, "1891": 7, "1938": 2730, "1985": 18391, "1911": 5945, "1947": 2291, "1921": 3627, "1888": 5, "1963": 11153, "2016": 32, "1895": 120, "1964": 11416, "1977": 14038, "1984": 16571, "2008": 122861, "1997": 38955, "1955": 8007, "1900": 1816, "1989": 21312, "1966": 13711, "1967": 14601, "1950": 4763, "1918": 3781, "1890": 6, "1931": 2507, "1986": 19440, "1905": 800, "1919": 3613, "1960": 11121, "1899": 1787, "1943": 1960, "1969": 14349, "1974": 13736, "1988": 19861, "2007": 119565, "1935": 2467, "1959": 10517, "1903": 2618, "1926": 2847, "1916": 5835, "1978": 14428, "1937": 2795, "1993": 26775, "1908": 2712, "2004": 84593, "1996": 36509, "1924": 2615, "2006": 108429, "1953": 6834, "1952": 6346, "2019": 2, "1941": 2206, "1970": 15000, "1987": 20122, "2011": 160017, "1934": 2493, "1991": 23799, "1946": 1965, "1998": 46583, "1933": 2433, "1897": 1309, "1956": 8628, "1928": 2773}
\ No newline at end of file
hw2/0.sql deleted 100644 → 0
/*Calculates the average the gpa for each major over all students/
hw2/1.sql deleted 100644 → 0
/*Find the bottom 10 majors in terms of average gpa (the majors from 0.sql that have the 10 lowest GPAs).*/
hw2/2.sql deleted 100644 → 0
/*For each major, calculate the fraction of students who have a 4.0.*/
hw2/3.sql deleted 100644 → 0
/*Find the college that contributed the most number of students.*/
hw2/4a.sql deleted 100644 → 0
/*Write a query to find all the distinct cities in the hometown table that have the same name.*/
hw2/4b.sql deleted 100644 → 0
/*Calculate the number of colleges per-capita (total divided by the population) in each state.*/
hw2/5.sql deleted 100644 → 0
/*The number of unique cities in the hometown table that don't have any students in the database.*/
hw2/6.sql deleted 100644 → 0
/*List the names of each student with the highest gpa in their home cities from those cities where there are at least 8 students from that city.*/
hw2/README.md deleted 100644 → 0
# SQL Exercises
*Due 5/13/19 11:59 PM*
In this assignment, you will practice writing SQL queries against a synthetically generated
"Graduate Admissions" database. This database contains three tables: a table of students, a table of undergraduate institutions from which they came, and a table of cities from where the students attended high school.
The tables are defined as follows: