### Description

These ExternalAttrib scripts estimate AVO intercept and gradient based on Shuey's 2 term approximation to the Zoeppritz equation.

### Intercept and Gradient from 4 Angle Stacks

**Script: Miscellaneous/ex_angle_stacks_4_to_AVOIG.py**

Takes as input 4 angle stacks and the corresponding angles and fits a least squares line to the amplitude and $ sin^2(angle) $ at each sample point. Ouput includes the intercept, gradient and the correlation coefficient of the line fit.

#### Input Parameters

For each input volume the corresponding incident angle must be provided.