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日期:2019-05-31 11:23

University of Western Ontario, Computer Science Department

CS1026A SU19, Computer Organization

Assignment 3 Due: May 31, 2019

General Instructions: This assignment consists of 4 pages, 1 exercise, and is marked out

of 100. Assignments are the independent work of each student. Software may be used to

detect cheating.

Non-Functional Code Instructions:

1. Include brief comments in your code. Identifying yourself (the code’s author) by name

and user ID in the initial comment header. Comment also on key instructions and

calculations in your code.

e.g. ##

# A program for parsing CSV files.

# Student Name: Alex Brandt

# Student ID: abrandt5

2. Follow good coding style and normal Python conventions. This includes, but is not

limited to:

(i) Meaningful variable names.

(ii) Conventions for naming variables and constants.

(iii) Use of constants over “magic numbers”.

(iv) Readability: indentation, appropriate white space (blank spaces) within instructions,

consistency in the use of all of the above.

Evaluation:

1. Functional Requirements:

(i) Does your module correctly implement the six statistical functions?

(ii) Does your main program behave according to the specifications?

(iii) Does your main program handle invalid input?

(iv) Does your main program output the files according to the specifications?

2. Non-Functional Requirements (above).

3. Ability to follow directions precisely.

Submission Instructions: Your submission should include exactly two files (zipped into

a zip file, if you’d like). These two files are: myStatistics.py and userid_main.py where

userid is replaced by your UWO User ID (everything preceding “@” in your UWO email; e.g.

abrandt5). The contents of these two files are described below.

Learning Outcomes: In this assignment we will look at using functions, dictionaries, lists,

and file I/O.

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Exercise 1. This problem deals with parsing numerical data and performing simple statistical

analysis. Imagine this scenario. Your chemistry lab-mate has collected many measurements

of an experiment and has put them all into a single file for you. This file is named

A3-data-file.txt and is posted on OWL alongside these instructions. It is now your job to

analyze the results. In this experiment there were four distinct trials and you must perform

the analysis on each trial individually. Unfortunately, your lab-mate has mixed data from

different trials together! Fortunately, each measurement has a label to indicate of which trial

it is a part. For example, the first few lines of the data file are:

trial1 123.43

trial3 341.32

trial2 123.42

trial4 89.337

trial3 355.12

Therefore, your program must perform the analysis of the data in three steps:

1. Read the data in the file and sort each measurement based on which trial it is a part.

2. Perform the statistical analysis on each trial.

3. Write the statistical analysis of each trial to new file (i.e. write out four different files).

To perform these three steps your program should be broken into two parts.

Part 1. In this section we will define the contents of the myStatistics.py file. In this

file we look to implement six functions for statistical analysis: myMin, myMax, myAverage,

myMedian, myStandardDeviation, myCountBins.

For all functions do not use Python’s statistics package nor the built-in min, max

functions. You must implement the math yourself.

myMin is a function which takes as its only parameter a list of floating point values and

returns the minimum value among all values in the list.

myMax is a function which takes as its only parameter a list of floating point values and

returns the maximum value among all values in the list.

myAverage is a function which takes as its only parameter a list of floating point values and

returns the average of all values in the list.

myMedian is a function which takes as its only parameter a list of floating point values and

returns the median of the values in the list.

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myStandardDeviation is a function which takes as its only parameter a list of floating point

values and returns the standard deviation of the sample of values. Standard deviation

can be computed by the following formula:

where are the individual values in a list of values, andˉ is the average of the list of values.

myCountBins is a function which takes two parameters: a list of floating point values, and

an integer number. This second parameter is the bin size. This function will implement a

simplified form of data binning https://en.wikipedia.org/wiki/Data_binning. This function

will go through the list of values given as the first parameter to count the number of values

in the list which fall into a certain “bin”. The bins are defined as: until all values in the input list

have been found to exist in a certain bin. For example, if the maximum value in the input list

is 30 and the bin size is 10 then there should be 4 bins: 

All functions only need to handle lists of floating point numbers. That is to say, if you

come across a non-number in the input list then your program is allowed to crash. The

myCountBins function only needs to handle non-negative numbers in its input list. All

other functions must handle all possible floating point numbers.

Part 2. In this section we define the contents of the userid_main.py file. In this file you

shall import your other file (e.g. by the command from myStatistics import *) and then

use those imported functions within your main function to prompt the user for the name of

the data file, read the data in that file, and then output the results of the analysis to four

different files. In particular, your main function should:

1. Prompt the user to input the name of the file which contains the data to analyze.

2. Open the file for reading, if possible. If the file is not found or not available for any

reason, simple print an error message “Sorry, the file <filename> is not available” and

then terminate the program.

Hint: use try: except: to accomplish this.

3. Read all of the data in the file and separate the data into four different lists, one list

for each trial.

Hint: A dictionary of lists would be very helpful here!

4. For each trial compute, using your myStatistics module,

the minimum,

the maximum,

the average,

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the median,

the standard deviation, and

the list of bin counts for a bin size of 25.

5. For each trial we wish to output the computed data to the files trial1-data-analysis.txt,

trial2-data-analysis.txt, trial3-data-analysis.txt, and trial4-data-analysis.txt

where trial1 data goes in the file trial1-data-analysis.txt, etc. The data should be

output in the following format where each item inside angled brackets (e.g. <minimum>)

is replaced by the actual value computed for that trial. All numbers should be printed

using 5 digits after the decimal place, except for bin_count which can simply be the

string representation of the list of counts.

minimum : <minimum>

maximum : <maximum>

average : <average>

median : <median>

std_dev : <standard deviation>

bin_count: <list of bin counts>

An example output file can be found on OWL next to these assignment instructions

but is also repeated here as an example. trial1-data-analysis.txt should have the

following contents:

minimum : 0.47074

maximum : 398.21285

average : 207.06971

median : 209.04432

std_dev : 115.91112

bin_count: [16, 12, 16, 15, 18, 19, 16, 13, 13, 12, 29, 11, 19, 14, 19, 19]

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