graphs_title.gif (2805 bytes)

You would not believe the fuss people make about graphs. 'They must be done in ink/pencil, must fill the (arbitrary) page, axes must be in ink and the line in pencil...' - all the sorts of daft rules that teachers love.

Graph plotting is an art, which is why I don't let my students use computers to do it. Once they've served their apprenticeship, fine, but not until then. The essentials in my scheme are

  • the graph should be pleasantly proportioned; this means axes of equal length or in a ratio of roughly 2:3, either landscape (page sideways on) or portrait (page normal);
  • the axes should be ruled and have sensible divisions; this means each square is 1, 2, 5 or 10 units (or multiples or sub-multiples). Don't use 3 or 7 units per square! You will mis-plot the points. Graphs take a long time for relatively small return, so make the plotting as easy, therefore as fast as is possible.
  • the points must remain visible once the line is drawn; use crosses, or dots with circles, or if you know the error magnitudes, error bars;

BE CLEAR about the nature of your graph - does it represent a continuous relationship needing a smooth curve, or a discontinuous one (e.g. something like ionisation energy plotted against atomic number), where the lines joining the points should be straight? Make sure you know before you join up the points.


Profit.wmf (5238 bytes)

Exam tips index      Home page