# CCNC/CCNC Module 4/Creating charts and graphs/About charts and graphs

Even though Calc will be performing the task of creating the charts and graphs, it is still important for you then user to have a clear understanding of the tools being created and the functions they perform. Thus this subsection provides a brief explanation of these data presentation tools. Charts and graphs provide us with a visual display of mathematical information. They are diagrams that show how two or more sets of data are related. By showing different sets of data in relation to one another, they make it possible for the person reading the data to observe patterns and trends, to make comparisons. Overall, charts and graphs allow for interpretation of the data.

The most commonly used charts are pie charts, bar charts (sometimes referred to as bar graphs) and histograms. The most commonly used graph is the line graph. A brief explanation of each of these is given below. These explanations were extracted and/or adapted from the website OpenLearn Learning Space, which we will return to later.

A pie chart is a diagram in the form of a circle that is subdivided into segments representing the elements of a whole. The size of each segment represents the proportion of that segment in relation to the whole. A pie chart is a good method of representation if we wish to compare a part of a group with the whole group.

Bar charts show data in the form of bars, with each bar presenting information about a particular item. The chart as a whole reflects the relationship between the items of information in terms of size: the bars get taller as the amounts being shown increase. The data presented through these separate bars are known as discrete data. In numerical terms, these data are presented as whole numbers, such as the number of eggs, children, laptops.

Histograms are a special form of bar chart or graph, in which the bars touch. The data are now referred to as continuous data. In other words, the data changes gradually along some sort of a scale, for example weight, height, temperature, or length.

A graph is a visual representation of data that shows the relationship among variables. The most commonly used graph is the line graph that compares one value of a variable as it changes with another value. Examples of pairs of variables are month of year and rainfall, school and test score average, and gender and careers. A line graph is constructed on two axes, known as the x-axis or horizontal axis and y-axis or vertical axis. The values of each variable are plotted on the respective axes.

You can learn more about charts and graphs through the following link: OpenLearn Learning Space: Working with charts, graphs and tables.  (accessed 15 December, 2007).