# About analysis variable algorithms

Analysis variables are loosely defined in Echoview as variables exported when analyzing acoustic data. Some can also be displayed in a dialog on screen. See About analysis variables for definitions of these variables. In this section we aim to specify the method by which the more complicated of these analysis variables are calculated.

Analysis variables are calculated over a domain or set of data points that is usually defined by a cell, region, selection or region-cell intersection.

Algorithms are provided for the following integration variables:

ABC and NASC

ABS

Aggregation_index

Center of mass

Depth_mean and Range_mean

Density_number

Density_weight

Equivalent_area

Fish_number

Fish_weight

Inertia

Kurtosis

N_sigma_bs

Ping_M

PRC_ABC and PRC_NASC

Proportion_occupied

Sample_mean

Samples

Sv mean

Skewness

Thickness_mean and Height_mean

Volume_integration

Wedge_volume_sampled