# 3.2 Example: Dotplot of oyster sizes

Let's re-visit the data on oyster sizes ({{@954#bkmrk-anderson1992}},{{@954#bkmrk-andersonunderwood1994}}). We have already seen some variation in the ***cumulative distributions*** of sizes of oysters settling on different types of substrata (see section [2.2](https://learninghub.primer-e.com/link/1021)). To compare these different distributions as densities, side-by-side, we'll compare the groups visually now, using a dot plot. The full set of data are contained in the file '<ins>Quibray_oyster_sizes.pri</ins>', found in the <ins>'Quibray_oysters</ins>' folder in '<ins>Examples_P8</ins>'. Each row of the data file contains the length measurement for an individual oyster (in mm), and the factor '<ins>Substratum</ins>' identifies the type of surface (concrete, marine plywood, fibreglass or aluminium) to which each measured oyster was attached.

#### Create a dot plot

Open the data in PRIMER and, if you like, you can see the factor of '<ins>Substratum</ins>' by clicking on **Edit** > **Factors** (then click '**OK**').

[![01._Quibray_oysters_full_+_factors_[i].png](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/scaled-1680-/01-quibray-oysters-full-factors-i.png)](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/01-quibray-oysters-full-factors-i.png)

To obtain a dot plot, from the '<ins>Quibray_oyster_size</ins>' data sheet, click **Plots** > **Dot Plot...**

[![02._Dotplot_dialog_[i].png](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/scaled-1680-/02-dotplot-dialog-i.png)](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/02-dotplot-dialog-i.png)

You will want to nominate the factor of '<ins>Substratum</ins>' here for the 4 different groups, then click '**OK**', as shown below.

[![03._Dotplot_dialog2_[new].png](https://learninghub.primer-e.com/uploads/images/gallery/2025-09/scaled-1680-/03-dotplot-dialog2-new.png)](https://learninghub.primer-e.com/uploads/images/gallery/2025-09/03-dotplot-dialog2-new.png)

The resulting graphic is a dot plot showing the sizes of oysters (specifically, their lengths in mm) measured from the four different types of substratum.

[![04._Dotplot_oysters_[i].png](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/scaled-1680-/04-dotplot-oysters-i.png)](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/04-dotplot-oysters-i.png)

From this, we can see that there tended to be more oysters at larger sizes on concrete surfaces compared to the other types of substrata. There were also fewer small-sized oysters on fibreglass surfaces compared to the other types of substrata. 

#### Change the axis label orientation

If you like, on this plot (or on any other plot), you can change the orientation of the labels identifying the groups on the x-axis. For this example, we might prefer to see the names of the different substrata displayed horizontally (i.e., parallel to the axis) instead of vertically (perpendicular to the axis). This is a new feature in PRIMER 8.

To do this, just click on the axis itself within the graphic and a context-specific dialog window (corresponding to the 'X axis' tab of the 'Graph Options' dialog) will pop up. This dialog window can also be obtained for this graphic by clicking on **Graph** > **General...** and then clicking on the 'X axis' tab.

In this 'Graph Options > X axis' dialog, inside the box entitled 'Label Orientation', choose $\bullet$Parallel, as shown below:

[![05._Parallel_x-axis_labels_[new].png](https://learninghub.primer-e.com/uploads/images/gallery/2025-09/scaled-1680-/05-parallel-x-axis-labels-new.png)](https://learninghub.primer-e.com/uploads/images/gallery/2025-09/05-parallel-x-axis-labels-new.png)

Click 'OK', and the revised graphic (with the x-axis labels now parallel to the axis) will then appear as follows:

[![06._Dotplot_oysters_parallel_x-axis_labels_[i].png](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/scaled-1680-/06-dotplot-oysters-parallel-x-axis-labels-i.png)](https://learninghub.primer-e.com/uploads/images/gallery/2025-12/06-dotplot-oysters-parallel-x-axis-labels-i.png)