This function computes the Symmetry-Adjusted Mean (SAM) between two values, typically representing the left and right measurements of a structure. SAM is a combined metric that incorporates both the average value and the asymmetry between the two sides.
asam(left, right, weight = 1)Numeric value representing the Symmetry-Adjusted Mean (SAM).
The formula is: $$ASAM = \frac{Left + Right}{2} - |Left - Right|$$
This metric captures both the overall size (average) and the degree of asymmetry between the two sides.
Consider a comparison between two groups (e.g., Control and Disease) where you want to assess differences in both the size and symmetry of a structure, such as the left and right hippocampus:
In the Control group, where symmetry is expected, SAM will be close to the average of the two sides.
In the Disease group, where asymmetry is expected, SAM will be lower due to the subtraction of the absolute difference between the left and right sides.
This metric is insightful because it combines information about both the structure's size and symmetry, allowing it to reflect differences in both characteristics.
# Example usage:
left <- 5
right <- 3
asam(left, right)
#> [1] 2
# For a symmetric case:
asam(5, 5)
#> [1] 5