This option can be accessed from the Data Analysis option on IFs Main Menu.
This screen looks much like others you have seen. One difference is that you must select a single or a small set of countries for your longitudinal analysis. You can look at a variable over time (using time as the independent variable), or you can treat time as points on the graph and look at the relationship between two variables.
Pick a variable such as AIDDon%GNI (aid donations as a percent of Gross National Income, the successor concept to Gross National Product). Using the screen that comes up when you touch Select Countries, pick the United States as a donor country. Then Exit back to the screen for analysis over time and Plot the result. You will see the decline in U.S. aid commitment over time.
On this particular plot, and dependent on the version of the model you are using, you may see values for Earliest and MostRecent. These values have been entered into the data file so that users can have available; for example, the most recent value of a variable for all countries, regardless of whether that value comes from 2000, 2001, or 2005. Most recent (and earliest) values are especially useful for cross-sectional analysis and you may or may not want them on your longitudinal graph.
Another feature of this section of IFs is the Computations button.
Exploration of maps, cross-sectional and longitudinal relationships, and relationships computed for IFs can give you much information about the apparent relationships among a wide range of global development indicators. Even if you never used IFs for forecasting, this data analysis capacity could significantly enhance your understanding of the world.