15.4 Add customised values/labels to graphical axes

In PRIMER 8, there is a new tool that allows us to add customised values and labels to coordinate axes in graphics.

Consider the following scatter plot of species richness ($S$) vs. structural complexity of the substratum (measured using a chain-and-tape method), obtained from a visual survey of intertidal macrofauna and algae at a site inside the marine reserve at Long Bay, on the north shore of Auckland, New Zealand.^¶ Biotic data ('Long_Bay_intertidal_biota') and environmental data ('Long_Bay_intertidal_env.pri') from this study are found in the 'Examples_P8' > 'Long_Bay_intertidal' folder.

In the above scatter plot, the points that correspond to the minimum ('Min') and maximum ('Max') values obtained for the variable of 'Complexity' (on the x-axis), have been labeled individual (using a factor that is empty for all other samples). We might decide it would be useful to annotate the graphic to provide the minimum and maximum values on the x-axis for those two values directly as well. We can do this by clicking on the x-axis (or by clicking Graph > General... and clicking on the 'X-axis' tab).

In this dialog, we can see an 'Additional Labels' button (), which is new in P8. We can also see the new option to change the label orientation so that it is either '$\bullet$Perpendicular' or '$\bullet$Parallel'. For the present example, let's choose '$\bullet$Parallel' and then go ahead and click the 'Additional Labels' button where we can add both the specific values and the desired labels for the maximum and minimum complexity, also including a tick-mark for each of them, like so:

The resulting graphic looks like this:

There are clearly many uses for this new feature. It is a great way to provide clarity regarding any specific values (or sets of values) that you may wish to highlight along particular axes in customised graphics.

Change the axis label orientation

Note that another new feature in PRIMER 8 is the possiblity to change the orientation of the axis labels. See section 3.2 for an example.

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^¶These data were collected in 2015 as part of a course in quantitative marine ecology at Massey University, Albany, New Zealand. Taxa that were recorded in the survey as 'dead' (e.g., oyster shells, barnacle tests, etc.) were not included in the tally of richness analysed here.