In Part 20, let’s see how to create mathematical expressions for your graph. Mathematical expressions on graphs are made possible through expression(paste()) and substitute()...

Today we see how to set up multiple graphs on the same page. We use the syntax par(mfrow=(A,B))..

Time Series are economic or other data that are collected over an extended period of time. Many clever methods have been developed to analyze time series, both to understand the factors that cause variation and to forecast future values.

One of those “rules” about statistics you often hear is that you can’t interpret a main effect in the presence of an interaction. Stats professors seem particularly good at drilling this into students’ brains. Unfortunately, it’s not true. At least not always.

You may have heard of McNemar tests as a repeated measures version of a chi-square test of independence. This is basically true, and I wanted to show you how these two tests differ and what exactly, each one is testing.

On my first assignment using Stata, I think I spent four or five hours trying to present my output in a “professional” form. The most creative method I heard about in class the next day was to copy the contents into Excel, create page breaks and then copy into Word. SPSS makes it so easy to copy tables and graphs into another document. Why can’t Stata be easy? Anyone who has used Stata has gone through this and many of you still are. No worries, help is on the way!..

We've already discussed using macros in Stata to simplify and shorten code. Another great tool in your coding tool belt is loops. Loops allow you to run the same command for several variables at one time without having to write separate code for each variable. This discussion could go on for pages and pages because there is much you can do with a loop...

We finished the last blog with the confusing coding of: local continuous educatexper wage age foreachvar in `continuous'{ graph box `var', saving(`var',replace) } I admit it looks like a foreign language. Let me explain how simple it is to understand..

Most statistical software packages use a spreadsheet format for viewing the data. This helps you get a feeling for what you will be working with, especially if the data set is small. But what if your data set contains numerous variables and hundreds or thousands of observations? There is no way you can get warm and fuzzy by browsing through a large data set. To help you get a good feel for your data you will need toutilize your software’s command or syntax editor to write a series of code for reviewing your data. Sounds complicated...

ROC Curves are incredibly useful in evaluating any model or process that predicts group membership of individuals. ROC stands for Receiver Operating Characteristic. This strange name goes back to its original use of assessing the accuracy of sonar readings. Any ROC can tell you how well a process or model distinguishes between true and false positives and negatives.