This is the code for an app which:

1. builds an Ordinary Least Squares (OLS) model,
2. checks the statistical properties of a model,
3. visualizes:
   1. the histogram of errors,
   2. the observed vs. predicted values,
   3. the predicted and observed values vs time (if a target variable is a time series).

The app is available here: https://dgwozdz.shinyapps.io/ols_app/