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# Graphic Presentation Handbook: Graphs

Click on the headings below to browse through the *Graphs *chapter:

__Graph types and their uses__

__Graph types and their uses__

*Scattergrams*

*Scattergrams*

**Figure 1. **Breaking distances for vehicles travelling at 80km/h (Author date[1])

*Line graphs*

*Line graphs*

**Figure 2.**Population growth within continents over the next 40 years (PRB 2009)

*Area graphs*

*Area graphs*

**Figure 3.** Changes in heavy metal contamination in Brisbane’s drinking water since the addition of the DSGT treatment plants (Author date)

*Bar graphs*

*Bar graphs*

**Figure 4.**2008 Populations in Australian States and State Capitals (NSW Government 2008)

*Histograms*

*Histograms*

**Figure 5. **Grades achieved by GEOM1000 students, semester 1 2009, St. Lucia, UQ (Author date)

*Population pyramids*

*Population pyramids*

- Males are shown on the left and females on the right, and are labelled as such
- Age groups are given in 5 year intervals
- Populations can either be presented as absolute values or percentages. If you are using percentages, they must reflect the total population (not the population within each sex).
- The same scale must be used to represent male and female populations
- Gridlines should be used for the X-axis so that the reader can estimate population values

**Figure 6. **ERP and Composite Estimate of Indigenous Australians in the Peninsula ATSIC region, 1996 (Taylor and Bell 2002)

*Pictographs*

*Pictographs*

**Figure 7.**Membership numbers for after-school clubs (Harcourt School Publishers n.d.)

*Pie graphs*

*Pie graphs*

- Structure pie graphs so that the largest segment begins at 12 o’clock, with the remaining segments running clockwise in decreasing order.
- Label each segment of the pie with either the total value or percentage. If you label with percentages, be sure to provide the total value somewhere in the graph so that the reader can convert the percentages (should they wish to).
- Use different shading or patters for each pie segment, as this will create contrast and improve readability.

**Figure 8. **Sales at The Fruit Market, Brisbane 2009 (total sales = $450 000) (Author date)

*Double-axis graphs*

*Double-axis graphs*

**Figure 9.**Earth’s climate history as reconstructed from Antarctic Ice Cores (McInnes 2009)

__Essential graph features __

__Essential graph features__

*Title*- Graphs have succinct yet comprehensive titles that inform the reader about their content. Graph titles are placed*beneath*the graphic as a caption (so if your computer program automatically places a title at the top of a graph, you must drag it to the bottom). The title should not simply repeat the axes labels, or contain the words “Graph of” or “Plot of”.*Axis labels*- Both the x (horizontal) and y (vertical) axes must have a label to indicate which variable they represent, and if necessary the unit of measurement into which the variables are divided. Origins should always be labelled on graphs (unless a logarithmic scale has been used, as the log of zero is not defined).*Tick marks*-Tick marks are used to indicate the scale of the graph. Major tick marks are labelled with a number, symbol or word, depending on the type of data being presented.Minor tick marks are placed within the major tick marks and are not labelled. They are designed to help the reader estimate detailed values off a graph (should they wish to).*Source*- Reference the source of your graph in the style consistent with the textual component your report. The reference should either be placed in the title or beneath the title in a source line.*Legend**(if presenting multiple variables)*- Legends are used to indicate the meaning of the shading and/or symbology used in a graph. They should be enclosed by a border, given a title and placed to the right of the graph, below the graph, or if small enough they can sit within the plot area.

__Customising your graphs__

__Customising your graphs__

*shading, scale, symbology*and

*labelling*to suit the type of data being presented and the style of your paper:

*Shading*

*Shading*

- Graphs should be shaded using subtle colours and hatching.
- The type of shading used in a given graph should be chosen to suit the data it contains, and the style of your paper.
- Bear in mind that the rule of thumb is to present graphics using the least amount of ink necessary.

*Scale*

*Scale*

- Graph scales should be chosen to suit the range of data values so that the data fills up as much space of the graph as possible.
- When the range of data in your graph is very large, it is best to use a logarithmic scale in the relevant axis (or axes).
- If you are beginning an axis with numerical markings on a point other than zero, you should indicate this clearly in the graph label.

*Symbols*

*Symbols*

- Symbols should be used to represent different variables in graphs.
- Symbols need to be large enough to be legible, and able to be easily distinguished from one another.
- Bear in mind that certain symbols have inherent meaning, as do certain colours.

*Labelling*

*Labelling*

- Labels should all be placed in the same orientation so that the reader does not have to turn the page.
- Make sure your labels are sufficiently large so that they are legible.
- Use visual hierarchy to indicate levels of significance (e.g. use bold, italics, and larger font size to make the most important labels stand out).

__Additional considerations for graphs__

__Additional considerations for graphs__

*Units of measurement** *

*Units of measurement*

- To save time and space, the units of measurement used on your graph axes are indicated in the axes labels and enclosed in brackets.

*Gridlines*

*Gridlines*

- Gridlines are lines that extend from your tick marks across the length of your graph.
- It may be useful to include gridlines when you have a large or wide-ranging graph, and you anticipate that readers may have trouble reading values off the graph.
- Gridlines run behind the plotted data so that they do not obscure the graph, and are weighted finely.

*Presenting multiple variables*

*Presenting multiple variables*

- When presenting multiple variables, you need to use shading and symbols to represent different data classes.
- Use a legend to indicate the meaning of the shading and/or symbology used in the graph.
- It is recommended that no more than 4 data classes be presented in a single graph, as any more than this becomes confusing.

*Statistical analysis*

*Statistical analysis*

- If you have used statistical analysis in your graph, you should present all relevant equations and values either in the plot-area of the graph (providing there is sufficient space) or beneath the graph as notes.
- If you have used computer software to perform your statistical analysis, you will need to reference this.

*Error bars*

*Error bars*

- If you are presenting means (averages) of a variable in your graph, you should always include error bars to indicate the associated uncertainty of each mean.
- Note that the value of error bars is rarely the same for each mean. If your computer program automatically generates error bars of equal value it is likely they are incorrect.

** ***Using multiple graphs for data comparison*

*Using multiple graphs for data comparison*

- each graph must be presented at the same size and scale so that the reader can make direct visual comparisons;
- the graphs needs to appear on the same page if they are to be easily compared; and
- human eyes find it much easier to compare lengths than areas, thus it is recommended that you do not use do not use series of pie graphs, area graphs or stacked bar graphs to compare data sets.

*Last updated: Aug 27, 2012*

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