\\Win2k Aub Edu Lb\Files\Homet\Tfc01\My Documents\L01 Preparing Data

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  • 1. CHAPTER 1: PREPARING DATA 1. Types of Data Three kinds of datasets are distinguished:  Cross-Sections (Unit of observation varies, time of observation fixed) Observations  Year Growth Savings Middle East Afghanistan 2005 -5 0.3 0 : 2005 2 0.2 0 Lebanon 2005 1 0.1 1 : 2005 2 0.4 0 Zimbabwe 2005 -1 0.2 0  Time series (Unit of observation fixed, time of observation varies) Observations  Year Growth Savings Lebanon 2001 3.1 0.3 Lebanon 2002 2.8 0.2 Lebanon 2003 1.4 0.2 Lebanon 2004 2.1 0.3 Lebanon 2005 2.5 0.3 1
  • 2.  Panels (Unit of observations varies, time of observations varies) Observations  Year Growth Savings Middle East Afghanistan 2000 -5 0.3 0 : : 2 0.2 0 Afghanistan 2005 1 0.1 0 : 2 0.4 0 Lebanon 2000 -1 0.2 1 : : 1 0.4 1 Lebanon 2005 1 0.3 1 : : 3 0.2 0 Zimbabwe 2000 2 0.1 0 : : -1 0.05 0 Zimbabwe 2005 -5 0.01 0 2. Preparing Datasets – Practical Tips  In practice, you always want to keep a dataset as an Excel file, which you copy into a statistical analysis program.  In preparing your datasets, you often retrieve data in table form and you need to stack your observations.  For example, what you download looks like this 2006 2007 2008 Afghanistan a b c : : : : Lebanon d e f : : : : Zimbabwe g h i 2
  • 3. but you need it like this Country Year Observation Afghanistan 2006 a Afghanistan 2007 b Afghanistan 2008 c : : : Lebanon 2006 d Lebanon 2007 e Lebanon 2008 f : : : Zimbabwe 2006 g Zimbabwe 2007 h Zimbabwe 2008 i which means that you need to transpose your data first and then stack it.  Dataset building needs a little bit of practice.  The following macro does the stacking for you in Excel. 3
  • 4.  “Stacking Macro” for Excel (Example: 45 rows, 220 columns) Sub SORTY() ' ' Macro1 Macro ' Macro recorded 3/19/2004 by mm53 ' ' Keyboard Shortcut: Ctrl+d ' For i = 1 To 220 Range("B1:B45").Select Selection.Copy Dim x As Object Set x = ActiveCell x.Offset(45 * i, -1).Select ActiveSheet.Paste Application.CutCopyMode = False Columns("B:B").Select Selection.Delete Shift:=x1ToLeft Range("B1").Select Next i End Sub 4
  • 5.  A note on different software programs. In preparing datasets for use in “gretl”, make sure that all columns except the first contain numbers. Other programs, such as NCSS, are more tolerant in this regard and will also read columns with strings. This means that “gretl” requires for each regional dummy a separate column while NCSS could read different regions from one column. 5