Graphs JSS3 Computer Studies Lesson Note

A graph is a diagram showing the relationship that exists among variables and quantities (varies data), usually of two, each measured along one of a pair of axes at right angles. It may not be possible to plot a graph without value. The Excel spreadsheet provides the values that are plotted. 

Creating a Graph

To create a graph, you can either use the chart wizard or press the F11 key.

Types of Chart

Line graph

Histograms

Pie-charts

Legends

Line Graph

Line graphs are often used to plot changes in data over time, such as monthly temperature changes or daily changes in stock market prices. Line graphs have a vertical axis and a horizontal axis. If you are plotting changes in data over time, time is plotted along the horizontal or x-axis and your other data, such as rainfall amounts is plotted as individual points along the vertical or y-axis. 

Histogram

A histogram consists of tabular frequencies, shown as adjacent rectangles, erected over discrete intervals (bins), with an area equal to the frequency of the observations in the interval. The height of a rectangle is also equal to the frequency density of the interval. 

Pie Charts

Pie charts, or circle graphs as they are sometimes known, are a little different from the other two types of graphs discussed. 

For one, pie charts do not use horizontal and vertical axes to plot points like the others. They also differ in that they are used to chart only one variable at a time. As a result, it can only be used to show percentages. The circle of the pie chart represents 100%. The circle is subdivided into slices representing data values. The size of each slice shows what part of the 100% it represents.

Legends

A legend is used to identify each series in a chart. It contains on sample of the marker colour and pattern of each series. 

EVALUATION

Define chart.

List the various types of charts you are familiar with in MS Excel.