# Body elongation

Definition

Body elongation measures how much the subject’s detected shape differs from a circle.

note Body elongation is not available if your experiment is set to:

▪Center-point detection.

▪Color marker tracking.

▪Live Mouse Tracker (but see Stretch attend posture).

▪Center-point, nose-point and tail-base detection, with two subjects per arena tracked with Deep learning.

Calculation

1. The Body elongation measure E is calculated as follows:

Where:

▪x,y are the coordinates of the pixels of the subject's contour in the current sample.

▪xc and yc are the coordinates of the center of the subject.

2.The Body elongation value is smoothed at each sample using the optional Averaging interval.

Body elongation is expressed as a percentage and ranges from 0% (when the subject's shape is perfectly circular) to 100% (when the subject's shape is a line).

How to specify Body elongation

1.Click the Add button next to Body elongation and click the Body Elongation tab.

2.Enter the Averaging interval. This is the number of samples over which the running average elongation is based. The default value is 1, that is, the variable is not smoothed using the values of neighboring samples. See Averaging interval

3.Complete the procedure to add the variable. See Calculate statistics: procedure.

Notes

▪Body elongation is not calculated with Live Mouse Tracker data.