# Swap subjects

Aim

To exchange the identities of two subjects within one sample (or range of samples, or the entire track), after checking that these were assigned incorrectly by EthoVision XT.

Below: An example of subject identity swap. 1. before the swap (Subject 1 = yellow track. Subject 2 = red track). 2. Moment of subject swap; the mouse with yellow track becomes Subject 2 and the mouse with red track becomes Subject 1 (see the last samples exchanged between the yellow and the red tracks). 3. After the swap.

To correct the subject identity swap, swap the subjects for all samples beginning from time 2, up to a new swap (if present) where subjects are labeled correctly again.

notes

▪If a large number of samples contain body points assigned to the wrong subject, it may mean that the detection settings defined to discriminate between subjects are not optimal, or that you need to improve the lighting or the color marking of your setup.

▪You can click Save on the toolbar so that if you are editing many swaps and make a mistake, you do not loose your previous edits. See Saving the track edits.

Procedure

1.If you work with multiple arenas, choose first the arena in the Samples List.

2.Play the track until you find samples with wrongly-assigned subjects.

tip Play frame-by-frame to position the video when the first samples are swapped (see the figure below).

3.Select the sample (or range of samples) in which you want to swap the subjects. To do so, in the Samples List, double-click the time value highlighted in blue, then drag to select the rows corresponding to all the samples to swap. The last row selected should be immediately before the next swap (where body points are assigned correctly again).

important If you drag on the Time column, all subjects in the trial are selected. If you have more than two subjects (for example, three subjects and you want to swap Subject 1 and 3), do not drag in the Time column. Instead, select the cells of one of the two subjects to swap. In the next step you will be asked to select the other subject.

Result: The selected samples are highlighted.

tip To swap subject identity throughout an entire track, click the header for one of the two subjects (e.g. click the header Subject 1).

4.Click the Swap subjects button on the toolbar, or press D.

5.If you have more than two subjects, the Swap Subject window appears. Select Swap Selected Samples. Select the second subject of the pair you want to swap, then click Apply.

Result: The subjects in the selection are swapped. You can check this in the Samples List, where the coordinates and the area are swapped between subjects and for the rows selected.

Notes

▪To search for subject swaps, plot the dependent variable Distance moved in the Integrated Visualization. The peaks in the plot appearing for two subjects indicate a quick displacement of the body points, that is a suspect subject swap.

▪To quickly swap two subjects for just one sample, drag the mouse around the subject's body points in the video window. Make sure that the Track Editor only display one sample.

Then click the Swap subjects button .

▪In the Time column of the Samples List, the cell highlighted in blue corresponds to the sample highlighted in white in the video window.

▪If you select several samples and choose to have one sample every n-th visualized, you also swap the body points in the selected range that are not visualized.

▪In the Swap Subjects window, select Swap all samples to swap the subjects for the entire track length.