Knowledge Base

Merging Method for Heatmaps

Aim

To specify how data of different tracks are merged in one heatmap.

Procedure

1. Choose Analysis > Results > Plot Heatmaps, or in the Experiment Explorer, under Results, click Heatmap Visualization.
2. In the Heatmap Settings pane, click the Show/Hide tab. Choose one of the options under Merging Method.

Cumulated

Each sample in a track gets a weight equal to 1/sample rate. Therefore, the color of a pixel in the heatmap represents the total time that the subject's body point was at that location. Choose this option when you want to make a heatmap based on all the possible locations of the animals for a group of tracks. With this method, a subject's position is over-represented in tracks longer than others.

Mean

Each sample in a track gets a weight equal to 1/track length. The color of a pixel represents the average proportion of a track that is found at that location. Choose this option when you want to make a heatmap that represents the average distribution for that group, and you want to compare averages between two or more groups of tracks.

Example: Consider two tracks, recorded at 25 samples/s. One track is 10 samples long, the other 1000 samples long. The total track duration is 1010/25 = 40.4 seconds. A subject's center point is found at location P two times in track 1 (= 20% of track 1), and 100 times in track 2 (= 10% of track 2). When the two tracks are merged:

• With Cumulated, the color of pixel P represents a total time of (2 x 1/25) + (100 x 1/25) = 4.08 s. This means that, in total, 4.08 s / 40.4 s = 10.1% of the data points are at that location. The longer track has a greater weight in this calculation.
• With Mean, the color of pixel P represents [(2/10) + (100/1000)] / 2 = 0.15 = 15% of the track duration. This means that on average, 15% of the data points are at that location. Short and long tracks have the same weight in this calculation.

Notes

• Merging makes sense when two or more tracks share the same value of an independent variable chosen as a header. For example, two tracks with the same Treatment level = Control. If Control is one of the headers, the two tracks contribute to the same heatmap.

Customize the Heatmaps

Aim

To choose which text, arena feature or background image to be displayed with the heatmaps.

How to Access These Options

Click the Show/Hide button on the toolbar.

Show and Hide the Overlay Text

To facilitate orientation in a heatmap matrix, you can display the value of independent variables used to arrange the heatmaps, and the number n of tracks used to create the current heatmap: Merged heatmaps: [n].

1. From the Show/Hide menu, select Text Features.
2. Under View, select Show information if you want to see overlay text over the heatmap.
3. Under Text properties, choose the text Fill color and Opacity.

Note: Even when selecting Show information, the overlay text is not shown if that information is redundant. For example, independent variables are not shown when the heatmaps have headers; for the same reason, the Merged heatmaps: [n] text is not shown when heatmaps are based on single tracks.

Show and Hide Arenas, Zones and Points

1. From the Show/Hide menu, select Arena Features.
2. In the Arena Features window, choose the arenas, zones, zone centers and points of interest you want to view over the heatmap.
3. Select the feature outline color. Next, click OK.

Note: Arenas and zones are displayed as outlines, not semi-transparent regions like in the Track Visualization. Zone centers and points of interest are displayed as crosses.

Customize the Background of the Heatmap

1. From the Show/Hide menu, select Background.
2. Choose one of the following options:
   • Plain - by range minimum to have a uniform background that is the same as the color for the minimum value in the heatmap. To change the color, click the Colors tab in the Heatmap Settings window and change the option under Display.
   • Plain - custom to have a uniform background. Click the button next to this option to select a color. To select colors other than the basic ones, click the button Other.
   • Captured image to have the image captured in the Arena Settings as a background.

If a heatmap is based on tracks with different Arena Settings, it is displayed with the background in the color currently selected next to Plain - custom.

Zoom the Heatmap In/Out

You can find the Zoom in (Ctrl+.) and Zoom out (Ctrl+,) buttons on the toolbar. To fit all heatmaps on the screen, click the Fit all button. To zoom in/out to predefined percentages, from the Show/Hide menu, select Zoom level, and choose one of the values available (6% to 800%).