Warning: foreach() argument must be of type array|object, bool given in /var/www/html/web/app/themes/studypress-core-theme/template-parts/header/mobile-offcanvas.php on line 20

Write a program to plot a horizontal bar chart of student exam scores. Your program should get input from a file. The first line of the file contains the count of the number of students in the file, and each subsequent line contains a student's last name followed by a score in the range \(0-100\). Your program should draw a horizontal rectangle for each student where the length of the bar represents the student's score. The bars should all line up on their left- hand edges. Hint: Use the number of students to determine the size of the window and its coordinates. Bonus: label the bars at the left end with the students' names. Computewell Dibblebit Jones Smith

Short Answer

Expert verified
Read student data from a file and use `matplotlib.pyplot` to plot a horizontal bar chart with labeled bars.

Step by step solution

01

Understand the Problem

We need to read student names and their scores from a file, with the first line indicating the number of students. Then, we plot a horizontal bar chart where each bar's length represents a student's score. Bars should be labeled with students' last names.
02

Read Input File

Open the file for reading. Read the first line to get the count of students. Then, read each subsequent line to extract the student's name and score. Store these as a list of tuples or a dictionary for easy access.
03

Import Required Libraries

Use Python's `matplotlib` for plotting. Import `pyplot` from the `matplotlib` library to create and manage the plot. Additionally, import `numpy` if any numerical operations are required.
04

Prepare Data for Plotting

Extract the names and scores from the data structure into separate lists. These lists will be used for plotting the horizontal bar chart. Ensure names and scores align correctly.
05

Configure Plot Size

Use the number of students from Step 2 to set the size of the plotting window. This can be done using the `figsize` parameter in `pyplot` to ensure all bars fit well.
06

Plot Horizontal Bar Chart

Use `pyplot.barh()` method to plot horizontal bars. Pass the names and scores as parameters, ensuring the names align vertically on the y-axis.
07

Label Bars

Use the `pyplot.text()` method to add student names as labels at the left end of each bar. Align text for clarity.
08

Display the Plot

Utilize `pyplot.show()` to render and display the bar chart on the screen.

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

File Handling
In Python programming, file handling is an essential skill, especially for tasks involving data input and output. In the context of this exercise, you begin by reading data from a file. This file includes information like the number of students and their respective exam scores. The goal is to process this file effectively.

To read the file, you employ Python's built-in `open()` function. This function allows you to access the file's content in different modes, such as reading ('r'), writing ('w'), or appending ('a'). In our example, you'd typically open the file in 'r' mode. Once the file is open, you read the first line to determine how many students are in the list. This is crucial since it helps to prepare the plot accordingly.

As you proceed, each subsequent line in the file needs parsing to extract the student's last name and score. These pieces of data are then stored in a convenient data structure, like a list of tuples or a dictionary. By organizing data this way, you facilitate efficient data manipulation and visualization later on.
Data Visualization
The core of this exercise revolves around data visualization, specifically plotting a bar chart representing student exam scores. Visualization transforms numerical data into visual representations, making interpretation and insights much more accessible. In this scenario, you are tasked with creating a horizontal bar chart, where each bar's length correlates to a student's score.

Start by preparing your data. Extract names and scores from your data structure into separate lists. This separation ensures that each name corresponds precisely with the right score. This alignment is vital, as mismatches can lead to incorrect visual outputs.

The next step is configuring the plot size, which depends on the number of students. Use the `figsize` parameter to ensure that all student bars fit neatly into the window. A correctly sized plot enhances readability and visual appeal. When plotting, it's essential to focus on clarity and accuracy to convey data effectively.
Matplotlib Library
Python's matplotlib library is a powerful tool for creating static, interactive, and animated visualizations. It's particularly valuable in data science and analytical tasks. In this exercise, you utilize matplotlib to generate a horizontal bar chart featuring student scores.

First, you need to import the library. Typically, you import `pyplot` from the matplotlib library as it provides a MATLAB-like interface for plotting. Additionally, you might import `numpy` if you require additional numerical operations, though it’s primarily optional here.

To create the horizontal bar chart, use the `pyplot.barh()` function. This function requires the student names and scores as arguments, and it arranges the names along the y-axis while the scores determine the bar lengths. For added clarity, you label each bar using `pyplot.text()`. This feature allows for the addition of names at the bar's left end, making the chart user-friendly.

Finally, rendering the plot with `pyplot.show()` displays the prepared visualization on the screen, enabling users to interpret the data visually with ease.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

A certain CS professor gives 5 -point quizzes that are graded on the scale 5-A, 4-B, 3-C, 2-D, 1-F, 0-F. Write a program that accepts a quiz score as an input and prints out the corresponding grade.

Word Count. A common utility on Unix/Linux systems is a small program called "wc." This program analyzes a file to determine the number of lines, words, and characters contained therein. Write your own version of we. The program should accept a file name as input and then print three numbers showing the count of lines, words, and characters in the file.

A Caesar cipher is a simple substitution cipher based on the idea of shifting each letter of the plaintext message a fixed number (called the key) of positions in the alphabet. For example, if the key value is \(2,\) the word "Sourpuss" would be encoded as "Uqwtrwuu." The original message can be recovered by "reencoding" it using the negative of the key. Write a program that can encode and decode Caesar ciphers. The input to the program will be a string of plaintext and the value of the key. The output will be an encoded message where each character in the original message is replaced by shifting it key characters in the Unicode character set. For example, if ch is a character in the string and key is the amount to shift, then the character that replaces ch can be calculated as: \\[ \operatorname{ch} r(\operatorname{ord}(c h)+k e y) \\]

Numerologists claim to be able to determine a person's character traits based on the "numeric value" of a name. The value of a name is determined by summing up the values of the letters of the name where "a" is 1, "b" is 2, "c" is 3, up to "z" being 26. For example, the name "Zelle" would have the value \(26+5+12+12+5=60\) (which happens to be a very auspicious number, by the way). Write a program that calculates the numeric value of a single name provided as input.

Write a program that counts the number of words in a sentence entered by the user.

See all solutions

Recommended explanations on Computer Science Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free