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A graphical representation is a visual display of data and statistical results. It is more effective than presenting the data in the form of tables. There are many ways to represent the data graphically such as bar graph, double bar graph, pictograph, line graph, linear graph, histogram, pie chart, etc.
A bar chart or bar graph is a chart or graph that presents the data with rectangular bars with heights or lengths proportional to the values that they represent. For example, if you want to present information on sales of cars during a period, you draw rectangles of the same width and height corresponding to the numbers representing the sales figures.
Let’s understand what is a bar graph and how is it read and how to make a bar graph using examples.
What is a Bar Graph?
A bar graph or a bar chart is a pictorial representation of grouped data. A bar graph shows the data with rectangular bars of the same width and the heights proportional to the values that they represent. The bars in the graph can be shown vertically or horizontally.
A bar graph is an excellent tool to represent data that are independent of one another and that do not need to be in any specific order while being represented. The bars give a visual display for comparing quantities in different categories.
The bar graphs have two lines, horizontal and vertical axis, also called the $x$ and $y$-axis along with the title, labels, and scale range.
Let’s consider an example of how does a bar graph looks like.
The bar graph shown above represents the sales of cars in a town during the period from 2000 to 2004. You can see the bar graph is drawn between two axes. The horizontal axis(or $x$-axis) shows the years and the vertical axis(or $y$-axis) shows the number of cars sold.
The rectangular bars drawn of the same width represent the sales of cars during the year corresponding to the bars. The length (or height) of each of the bars corresponds to the value(or the number of cars sold) during a year.
Let’s consider another example of the number of games played by tennis players in a particular year.
This bar graph also represents the same information related to sales of cars in a town during the period from 2000 to 2004. This bar graph is also drawn between two axes. The horizontal axis(or $x$-axis) shows the number of cars sold and the vertical axis(or $y$-axis) shows the years.
The only difference between these two bar graphs is that the first one is a vertical bar graph and the second one is a horizontal bar graph.
Types of Bar Graphs
Bar Graphs are broadly classified into two types depending on the orientation of the bars(rectangles):
- Vertical Bar Graph
- Horizontal Bar Graph
The bars in bar graphs can be plotted horizontally or vertically, but the most commonly used bar graph is the vertical bar graph. Either of these two categories can be of the following two types.
- Grouped Bar Graph
- Stacked Bar Graph
Vertical Bar Graphs
Vertical bar graphs are bar graphs where data is represented vertically in a graph or chart with the help of rectangular bars that show the measure of data. The rectangular bars are vertically drawn on the $x$-axis, and the $y$-axis shows the value of the height of the rectangular bars which represents the quantity of the variables written on the $x$-axis.
Horizontal Bar Graphs
Horizontal bar graphs are bar graphs where data is represented horizontally in a graph or chart with the help of rectangular bars that show the measure of data. In this type, the variables or the categories of the data have to be written and then the rectangular bars are horizontally drawn on the y-axis and the x-axis shows the length of the bars equal to the values of different variables present in the data.
Stacked Bar Graph
The stacked bar graph(or composite bar graph) divides the whole bar into different parts. In this, each part of a bar is represented using different colors to easily identify the different categories. It requires specific labeling to indicate the different parts of the bar. Thus, in a stacked bar graph every rectangular bar represents the whole, and each segment in the rectangular bar shows the different parts of the whole.
Grouped Bar Graph
The grouped bar graph(or clustered bar graph) is used to show the discrete value for two or more categorical data. In this, rectangular bars are grouped by position for levels of one categorical variable, with the same colors showing the secondary category level within each group. It can be shown both vertically and horizontally.
Properties of Bar Graph
These are some properties that make a bar graph unique and different from other types of graphs.
- All rectangular bars should have equal width and should have equal space between them.
- The rectangular bars can be drawn horizontally or vertically.
- The height of the rectangular bar is equivalent to the data they represent.
- The rectangular bars must be on a common base.
Advantages of Bar Graph
These are the advantages of bar graphs over the other types of graphs.
- Display relative numbers or proportions of multiple categories
- Summarize a large amount of data in a visual, easily interpretable form
- It makes trends easier to highlight than tables do
- Bar graphs help in studying patterns over a long period of time
- It is used to compare data sets. data sets are independent of each other
- It is the most widely used method of data representation. therefore, it is used in various fields
- Bar graphs estimates can be made quickly and accurately
- It permits visual guidance on the accuracy and reasonableness of calculations
- Bar graphs are very efficient in comparing two or three data sets
How to Read a Bar Graph
The different steps to read a bar graph are given below:
Step 1: Check whether the given bar graph is a horizontal bar graph or a vertical bar graph.
Step 2: In the case of a vertical bar graph, the categories are present on the horizontal axis (or x-axis) and the data values are represented by the vertical bars(or rectangles).
In the case of a horizontal bar graph, the categories are present on the vertical axis (or y-axis) and the data values are represented by the horizontal bars(or rectangles).
Step 3: For each category,
In the case of a vertical bar graph note down the point on the $y$-axis corresponding to the height of a vertical bar
In the case of a horizontal bar graph note down the point on the $x$-axis corresponding to the length of a horizontal bar
Examples
Let’s consider an example to understand how a bar graph is read.
Ex 1: Observe the bar graph and answer the following questions
- In which year maximum number of trees were planted by the eco-club?
- In which year the number of trees planted by the eco-club was minimum?
- In which two years, the same number of trees were planted. How many total trees were planted in those two years?
- How many total trees were planted by the eco-club between 2005 and 2010?
The longest bar(or rectangle) corresponds to the year 2008. Therefore, the maximum number of trees planted in the year 2008, and was 300.
The smallest bar(or rectangle) corresponds to the year 2009. Therefore, the minimum number of trees planted in the year 2009, and was 100.
The height of the bars corresponding to the years 2005 and 2010 is the same and is equal to 150. Therefore, between 2005 and 2010, each year 150 trees were planted each. The total number of trees planted in these two years was 150 + 150 = 300.
The number of trees planted each year is
During 2005, the number of trees planted = 150
During 2006, the number of trees planted = 250
During 2007, the number of trees planted = 200
During 2008, the number of trees planted = 300
During 2009, the number of trees planted = 100
During 2010, the number of trees planted = 150
Total number of trees planted by the eco-club between 2005 and 2010 were 150 + 250 + 200 + 300 + 100 + 150 = 1150
How to Make a Bar Graph
The different steps to make a bar graph are given below:
Step 1: First, decide the title of the bar graph.
Step 2: Draw the horizontal axis and vertical axis. (For example, Favourite Fruit)
Step 3: Now, label the horizontal axis.
Step 4: Write the names on the horizontal axis, such as Apple, Mango, Pineapple, Orange, and Grapes.
Step 5: Now, label the vertical axis. (For example, the Number of Students)
Step 6: Finalise the scale range for the given data.
Step 7: Finally, draw the bar graph that should represent each category of the fruit with their respective numbers.
Examples
Let’s consider an example to understand how a bar graph is drawn for the given data.
Ex 1: A group of students was asked about their favourite activities. The following table shows the data regarding the hobbies of the students. Draw a bar graph to represent the given data.
The first step is deciding the title of the bar graph. Let’s name our bar graph “Favourite Activities of Students”.
Next, draw the axes.
The horizontal axis represents the activity and the vertical axis represents the number of students.
To choose an appropriate scale, note down the minimum and maximum values in the data set.
The minimum value (Dance – Number of students = 5)
The maximum value (Drawing – Number of students = 30)
Since the maximum value is 30 and the minimum 5, so let’s mark the maximum point on the vertical axis as 35 starting from 0 with equal intervals of 5. This will fit all the values properly in the bar graph.
Finally, draw the bar graph that should represent each category of the activity with their respective numbers.
Practice Problems
In the library of a school, there are books on the following subjects in given numbers: English — 150, History — 300, Math — 500, Science — 325. Draw a bar graph for the given data.
Draw a bar graph for the given data
The number of students studying in each of the five classes of a school is given below. Draw a bar graph to represent the numerical data.
From a pond, the following numbers of fish were caught on different days. Draw the bar graph of it.
FAQs
What is a bar graph explain with an example.
A bar graph can be defined as a graphical representation of data, quantities, or numbers using bars or strips. They are used to compare and contrast different types of data, frequencies, or other measures of distinct categories of data. For example, the graph on the right shows the number of trees planted by eco-club during the years 2005 – 2010.
What is the difference between a bar graph and a histogram?
The major difference between a bar chart and a histogram is the bars of the bar chart are not just next to each other. In a histogram, the bars are adjacent to each other. In statistics, bar charts and histograms are important for expressing a huge or big number of data.
How do you represent a bar graph?
The rectangular bars in a bar graph can be drawn horizontally or vertically. In a bar graph, horizontal (or vertical) rectangular bars should have equal width and space between them. The height of the rectangular bars in a bar chart is equivalent to the given data it represents.
Conclusion
A bar graph shows the data with rectangular bars of the same width and the heights proportional to the values that they represent. The bars in the graph can be shown vertically or horizontally. These are very helpful in displaying relative numbers or proportions of multiple categories.
