One of the methods to visualize data in the OMA book chapters is regression charts, however there was no example or mention about it in the exercises chapter. 

I have added:

1. Regression Analysis under visualization heading after heatmaps (Line 1743)
2. Added description and steps for it.
3. Added an R code to do Regression analysis using package ggplot2 and lm() function.

1. Used the GlobalPatterns dataset from mia & compared against Shannon Index instead of individual taxa method. 
2. Checked assumptions such as linearity, normality, homoscedasticity, and independence of residuals.
3. Include sex as a secondary covariate in the regression model.
4. Used scater for PCA and visualization.
5. Added violin plot as well, for extra reference.

1. Introduced two examples : one with discrete x and one with continuous x against shannon index.
2. Made changes to the steps and interpretations accordingly while adding gtsummary and jtools for summary and coefficient visualization.

Removing the unused libraries from line 1796

Added description to the variable, coverage.
Edited the shannon method command.

eval : true, minor edits