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C++ Program to Draw Histogram

Introduction to Histograms and Their Use Cases

The frequency distribution of a collection of data is graphically represented using histograms. They are frequently used to visualize and analyze data in scientific research, statistics, and data analysis. A histogram comprises a sequence of vertical bars, where each bar's height denotes the frequency with which data values fall into a given range or bin.

When it comes to spotting patterns and trends in data, such as the existence of outliers or skewed distributions, histograms are extremely helpful. They can also contrast various data sets or examine the connections between various variables. Moreover, histograms can spot data gaps or inconsistencies needing additional research or analysis.

Histograms are used in a wide range of fields, including:

  1. Business and Economics - to analyze sales data, customer demographics, and market trends.
  2. Medicine and Biology - to analyze patient data, study disease prevalence, and track genetic traits.
  3. Environmental Science - to analyze air and water quality data, study climate patterns, and track environmental changes over time.
  4. Engineering and Physics - to analyze sensor data, study physical phenomena, and model complex systems.
  5. Social Sciences - to analyze survey data, study human behavior and preferences, and track social trends over time.

Histograms are a powerful tool for analyzing and interpreting data, and their applications are diverse and wide-ranging.

The Libraries Needed to Draw a Histogram in C++

  1. Standard C++ libraries:
    1. iostream: for input and output operations
    2. vector: for creating arrays and storing data
    3. algorithm: for sorting and counting elements in arrays
  2. Third-party libraries:
    1. Qt: a popular cross-platform application framework that includes a wide range of graphical tools for creating user interfaces and visualizations.
    2. OpenGL: a powerful graphics library that enables high-performance 2D and 3D graphics rendering.
    3. matplotlib: a Python library that can be used with C++ via Python-C++ bindings to create various types of visualizations, including histograms.

To draw histograms in C++, you can alternatively use various graphics libraries such as SDL (Simple DirectMedia Layer), Allegro, or SFML (Simple and Fast Multimedia Library). Your individual needs, such as the intricacy of the visualization, the performance requirements, and the preferred output format, will determine the library you use.

Understanding the Data Set to be Visualised

Knowing the data set is essential for producing a histogram since it enables you to choose the right range and bin size. Before making a histogram, consider the following steps to comprehend the data set:

  1. Determine the type of data - The best visualization technique depends on the type of data. For instance, a bar chart rather than a histogram could be more suited if the data is categorized.
  2. Identify the data's range - Determine the data set's minimum and maximum values. This makes it easier to choose the range of values that the histogram should include.
  3. Determine the total number of bins - The granularity of the histogram is determined by the number of bins. The histogram may lose significant data features if the bin size is too high, but if it is too tiny, the histogram may become overly noisy. The square root choice, which takes the square root of the number of data points to calculate the number of bins, is a widely used rule of thumb.
  4. Find the outliers - Search the data set for outliers, which are extreme numbers that could skew the histogram. These can be located and eliminated to provide a histogram that is more precise.
  5. Think about how the data are distributed - The histogram's shape might reveal information about how the data are distributed, such as whether it is symmetric or skewed. Finding trends and patterns in the data can be made easier by understanding the distribution.

You may make a histogram that accurately depicts the data and offers insights into its distribution and trends by comprehending the data set and taking into account the proper range, bin size, and the number of bins.

Defining the Variables and Constants for the Program

A crucial step in creating a C++ program to draw a histogram is defining the variables and constants for the program. The following are some examples of variables and constants you might define:

  1. Input Data - Create a variable to retain the input data, which may come from user input or a file.
  2. Number of Data Points - Create a variable to hold the entire amount of input data points.
  3. Minimum and Maximum values - Create variables to hold the input data's minimum and maximum values.
  4. Bin Size - Create a constant to represent the dimensions of each histogram bin.
  5. Number of bins - Create a variable to hold the histogram's bin count, which can be generated using the square root option or another suitable technique.
  6. Frequency of Each Bin - Create an array to keep track of how frequently data points fall into each bin.
  7. Maximum Frequency - Create a variable to hold the highest frequency for each bin so you can scale the height of the histogram bars afterward.
  8. ASCII Characters - Create a set of ASCII characters that each represent a specific range of frequencies in order to depict the histogram bars.
  9. Output Format - Specify any pertinent formatting choices, such as font size or color, as well as the output format, such as a console or graphical display.

You can write a C++ program that draws a histogram in a systematic and effective manner by specifying these variables and constants.

Steps to Draw a Histogram

The procedures for making a histogram in C++ are as follows:

  1. Read Data from File - Reading data from a file is the initial stage in the process of plotting data. Standard C++ input/output functions like ifstream and getline() can be used to accomplish this. Input from users may also be used to gather the data.
  2. Process Data - Data processing is required to ascertain the frequency of each value or range of values after the data has been collected. Several methods, such as counting sort or sorting algorithms, can be used to accomplish this. A data structure like an array or a map may be used to store the data.
  3. Determine the Number of Bins - The data range and required level of granularity of the histogram must be taken into consideration when deciding how many bins, or bars, should be presented in the histogram. Based on the total number of values and the maximum frequency, the width and height of each bar must be determined.
  4. Display the Histogram - After the data has been analysed, you may use a graphical user interface to view the histogram. Using graphic libraries like OpenGL or SDL, the bars can be drawn. The title, axis labels, and any other pertinent information should also be shown by the application.
  5. Add features: More features can be added to improve the program's usability and functionality. The application might be set up to take user input for parameters like the number of bins or the range of values, for instance. Users can hover over the bars in the program to see their frequency by making it interactive.
  6. Save the output: The application can be made to save the output in a file format like PNG or JPG after the histogram has been presented.

C++ program to Draw a Histogram


9|                  * 
8|                  * 
7|          *       * 
6|          *     * * 
5|      *   *     * * 
4|  *   *   *     * * 
3|  *   * * *     * * 
2|* *   * * * *   * * 
1|* * * * * * *   * * 
  1 2 3 4 5 6 7 8 9 10 


In this program, the function drawHistogram adds a row label (which is the current row value) to the left of each row of asterisks, and a column label (which is the current col+1 value) below each column of asterisks. The row labels are drawn before the asterisks, and the column labels are drawn after the asterisks, to ensure that they align correctly.

  • Time Complexity:

The given program has a time complexity of O(n * m), where n is the number of input vector items and m is its highest value. This is the result of the software iterating over each vector element to get the maximum value before drawing the histogram iteratively through each value from 1 to the maximum value.

  • Space Complexity:

The space complexity of the program is O(m), where m is the largest value in the input vector. This is so that the software can store each row of the histogram in an array of size m.

Note - The space complexity can be extremely high in the worst-case scenario, when the maximum value is very large relative to the number of items in the input vector, potentially causing memory problems.

Future Improvements

The following are a few advanced features that can be added to the application to improve its usability and aesthetic appeal:

Interactive Histogram Displays - By including user input, you may let users change the data and change how the histogram is shown. You could, for instance, provide user the option to add or remove data points, modify the x-range, axis or change the bin size.

Color-Coded Histograms - In a histogram, you might use various colors to represent various categories of data. For instance, you could use various colors to represent different age groups or male and female data points.

Customizable Axes - Axes that the user can configure include the labels, tick marks, and range of the x and y axes. As a result, the histogram would be more adaptive to various sorts of data.

Export Options - Options for exporting the histogram to multiple file formats, such as PDF or PNG, may be added. The histogram might then be quickly added by users to reports or presentations.

Multiple Histograms - By adding multiple histograms to the same graph, you may let the viewer compare various data sets. This would make it simpler to compare and analyse data.

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