Overview of Computer Graphics
One of the prime uses for graphical software at the University is to produce
graphs and charts.
Everyone has data of one kind or another, whether on paper, in the computer,
or just in the mind. We often need to know the significance and properties of
the data, or to be able to compare different parts of it against other data
One of the simplest aspects of data display is the production of charts. This
is where you would want to put your data into a graphical form to show
relationships and comparisons between sets of values. There may be a number of
reasons why you would want to put your data into a chart:
to illustrate differences between different sets of data
to show trends between two variables
to show patterns of behaviour in one variable.
There are basically two broad areas of graphs:
Presentation charts and graphs of the kind used to illustrate a few principal points. We see these on news and current affairs programs on television. A bar chart or a pie chart is used to indicate results of data obtained so far and the general trends. They are often liberally decorated with bright colours to increase their visual appeal and attractiveness to the viewers and to hold their attention. They are used for visual impact and getting a simple point over clearly and effectively.
Scientific charts and graphs are more concerned with ensuring that the detail in the data is represented accurately and faithfully. We may have some results obtained from experimental measurements and wish to display them. We may want to compare the results from the data measurements with the results we would expect according to a particular theoretical model. We may want to draw a curve through the data points (i.e. interpolate the data) and display this along with the original points.
The aims of the two are different, and so the facilities you will want from
your charting package will also be different.
Presentation charting has more to do with impressive presentation graphics
where the aim is to put a salient point across to an audience. As a result the
priority with this sort of charting is not always accuracy of representation.
You want charts with strong colours, an impressive look and special effects. The
effect of a presentation can be enhanced by using 3D graphs, adding pictures to
the graph, or using pictograms. These sorts of charts are rarely produced in
isolation but as part of a general presentation. Therefore, some presentation
packages also have their own charting module for this purpose. Word and
PowerPoint use a module called Microsoft Graph and Excel's
charting module has some very powerful presentation graphics features.
Origin and Gsharp, both dedicated charting packages, also provide
professional presentation charting facilities on the PC systems. Gsharp
is also available on the UNIX systems.
In scientific charting you want to display data as accurately as possible in
order to analyse it graphically or demonstrate clearly your comparisons and
results. As this sort of charting is done mainly for analysis, it is rarely an
isolated activity but is often done alongside detailed numerical analysis of
your data. Two of the most powerful charting packages available are
Origin on the PC network and Gsharp on the PC and UNIX systems.
Also, many numerical analysis packages have their own charting modules
integrated with the rest of the package.
It is clear that your choice of charting program will depend very much on
what purpose you want the chart to fulfil, and also what other programs you are
already using. On the whole, if you are already using a program that has its own
charting module, use that. The table below gives some rough guidelines on your
choice of charting PC package, with the packages increasing in facilities and
complexity going down the table.
Simple bar, column, line or pie charts to integrate in a word
Microsoft Graph in Word, Charting Module in Excel
Charts for use in a presentation
Microsoft Graph in Word or PowerPoint, Charting Module in Excel,
Raw data requiring good quality scientific charting
Data requiring simple mathematical or statistical analysis
Charting Module in Excel, Origin, Gsharp
Complicated statistical analysis and good quality scientific
Graphics module in SPSS
If you want to do charting on UNIX you are recommended to use the
Uniras software and in particular Gsharp.
Pages in Overview of Computer Graphics
- 1. Introduction
- 2. What are computer graphics?
- 3. You are here: Charting
- 4. Presentations
- 5. Drawing, Painting and Design
- 6. Computer aided design and drawing
- 7. Scientific visualisation
- 8. Desktop Mapping and GIS
- 9. Subroutine libraries for graphics
- 10. Multimedia
- 11. Further information
- 12. Appendix 1 Software Summary
- 13. Appendix 2 Computer Systems
- 14. Appendix 2 Peripheral Devices
- 15. Appendix 3 Graphical File Formats
- 16. Appendix 4 Graphics Terminology