Graphs An Introduction

1 / 13

# Graphs An Introduction - PowerPoint PPT Presentation

Graphs An Introduction. What is a graph?. A graph is a visual representation of a relationship between, but not restricted to, two variables.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Graphs An Introduction' - nikkos

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### GraphsAn Introduction

What is a graph?

A graph is a visual representation of a relationship between, but not restricted to, two variables.

A graph generally takes the form of a one- or two-dimensional figure. Although, there are three-dimensional graphs available, they are usually considered too complex to understand easily.

A graph commonly consists of two axes called the x-axis (horizontal) and y-axis (vertical).

A graph can show Discrete or Continuous data types. Data types determines which graph to use.

Discrete or Continuous

Discrete:

Data that can be separated by some interval, for example:

Recording the shoe sizes of a class – Bar graph

Continuous:

When data collected is continuous, for example:

Recording temperature – Line graph

This is a graph

25

Y – axis

Scale or Increments

20

All graphs (except Pie Chart) have common elements:

• Axis x and y (also z in 3D graphs)
• Axis labels
• A title
• Scales or Increments
• Can represent negative values

15

Y – axis label

10

5

Origin – does not always have to start at 0,0

X-axis

10

20

30

40

50

-20

-10

X-axis label

-5

Scale or Increments

-10

If we draw a vertical line from any point on the x-axis

Co-ordinates

25

Y – axis

and a horizontal line from the y-axis

20

A (3,15)

the point at which they meet gives us the co-ordinate

15

B (-4,10)

10

5

1

2

3

4

5

-5

-4

-3

-2

-1

-5

X-axis

-10

-15

C (-5,-15)

Back

Types of Graphs

Four basic types of graph or chart

Line

Pie

Bar

Scatter

See creating a line graph presentation

Line Graphs

A good method of showing the relationship between two variables

Back

Bar Chart / Graph

Used to compare values in a category or between categories.

The graph shown here makes a visual comparison of the fat content of types of cheese

Bar Chart / Graph

Can be useful to study trends over time

See creating a bar graph presentation

Bar Chart / Graph

Multiple (or group) bar graphs compare relationships of closely related sets

Back

See creating a pie chart presentation

Pie Charts

A pie chart is used to show how a part of something relates to the whole. This kind of graph is particularly suited to showing percentages

Back

Weight (kg)

Height (cm)

Scatter Graph

Drawing a scatter graph is similar to drawing a line graph in that co-ordinates are used to plot the points. There are usually more points to be plotted in a scatter graph and the points can be in groups, therefore it is not possible to draw a line through all of the points.

A scatter graph shows how much correlation there is between two variables that you suspect may be linked for instance height and weight as shown here:

It is sometimes useful to draw a “line of best fit” to show the trend

Line of best fit

Back

Summary

A good graph:

Accurately shows the data