Zipf's Law Microarray Normalization

The microarray normalization technique using Zipf's Law has been implimented as a Microsoft Excel macro.

     Download: ZipfsNormalize.xls

This implimenation has the following limitations:

• Does not handle missing data values.
• Excel is limited in the number of genes (rows) can be normalized:
  

  Excel 4.0	16,384 rows
  Excel 5.0	16,384 rows
  Excel 7.0 (aka 95)	16,384 rows
  Excel 8.0 (aka 97)	65,536 rows
  Excel 2000	65,536 rows

If you cannot live with these limitations, you may want to try the Perl script implimentation.

Installation

• Download the ZipfsNormalize.xls document.
• Open it in Excel.
• If a dialog box comes up asking if you want to activate macros, you do. Answer "Macros Activate"
• If you are not asked, and you are also not able to activate the macros, your security setting may be set too high. In the menu bar open Extras->Macro->Security and select a lower security level.

• Highlight the data you wish to normalize. DO NOT highlight the column or row headers, these will be copied to the normalized datasheet automatically. Alternatively, make the first data containing cell the active cell.
• In the menu bar, select Extras->Macro->Macros... (or by hitting Alt+F8)
• In the dialog box that appears, run the macro called ZipfsNormalization.
• Depending on how much data to be normalized and the proccessing power of the computer, you may have to wait for the completion of the normalization procedure.
• When normalization is finished, a new worksheet titled 'normalized data' is created in the workbook. This worksheet contains the normalized data and the identical column and row headers as the original data.

Importing raw text data with different formats can sometimes be a problem. For example, in Germany, commas are used as a decimal marker instead of the point. In the third window of the text import dialog, you can click on the 'more' button to choose the decimal separator. Also in the third window of the text importer, you may wish to specify the data format of the columns.

You may wish to modify or improve the macro for your own purposes. To do this, open the Visual Basic Editor by clicking Extras->Macro->Visual Basic Editor in the menu bar (or by hitting Alt+F11). For example, you may wish to see the ranks that were assigned to the genes in order to make a graph of the data. You can comment out the line of code that deleted the ranks as shown.

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Last updated: 01.05.2003