* SHAZAM Example: Modelling the rate of growth of expenditure in services 
* expenditure on durable goods using an OLS regression with generated
* variables and creating a graph
* Author: Skif Pankov
* 
* Source:
* Damodar N. Gujarati and Dawn C. Porter, Basic Econometrics - 5th Edition
* McGraw-Hill International Edition
* Chapter 6, Example 6.4 (page 163)
*
* Analytical Techniques Demonstrated:
*   Ordinary Least Squares (OLS) regression
*   Generating variables
*   Plotting a graph
*
* Description: We generate log and time variable, run an OLS regression 
* with generated variables and generate a graph
*
sample 1 15

* Read the datafile and name the variables - we use the same datafile as in 
* Example 6.3
read (data_6.3.shd) expserv expdur expndur pcexp

* Generating a log of expserv
genr lnexs = log(expserv)

* Generating a time index variable
genr T = time(0)

* Running an OLS regression of lnexs on T, stating that it is a log-linear
* model, stating to show residual statistics and saving predicted values 
* in a variable plnexs
ols lnexs T / rstat loglin predict=plnexs

* Creating a plot of plnexs against T
graph plnexs T

stop