1. AGB 260: Agribusiness Information Technology Importing Data, Managing and Transforming Data, Data Validation, and Handling Errors

2. Useful Chapters in the Textbook Regarding this Lecture  Chapter 26  Chapter 31  Chapter 32

3. Valuable Sources of Data  http://aic.ucdavis.edu/research/datasources.htm http://aic.ucdavis.edu/research/datasources.htm  http://www.ers.usda.gov/data-products.aspx http://www.ers.usda.gov/data-products.aspx  http://www.bls.gov/ http://www.bls.gov/  http://www.cdfa.ca.gov/statistics/ http://www.cdfa.ca.gov/statistics/  https://www.census.gov/ https://www.census.gov/

4. Importing Data  The data that you work with in Excel can be entered in a few basic ways.  You can enter the data by hand one data cell at a time which can be inefficient.

5. Importing Data Cont.  You can copy the data and try to paste it into Excel.  Fortunately, Excel has the capability to import many different types of data.

6. Importing Data Cont.  There are several sources you can import data from:  Access Database  From the Web  From Text  From other Sources

7. Copy and Paste  Sometimes you can input data into Excel by just copying it and then pasting it.  To do this, go to the source document, highlight the data, copy it, and then paste it into Excel.  Sometimes Excel is smart enough to enter the data correctly.

8. Copy and Paste  Other times it will bring the data in as a text in a single column.  Excel has the ability to turn data that is in a single column into data that spans multiple columns.  In class we will work with:  http://www.cdfa.ca.gov/Statistics/PD Fs/ResourceDirectory_2013.pdf http://www.cdfa.ca.gov/Statistics/PD Fs/ResourceDirectory_2013.pdf

9. Importing Data Through the Web  On the Data Ribbon under Get External Data, there is a button that allows you to get data from the Web.  When you press this button, Excel brings up a page that looks like a web page.  From here you can enter the web page that has the data you are interested in importing.

10. Importing Data Through the Web Cont.  Once you are on the web page, you will see yellow arrows and associated box around what Excel can import.  Click on the yellow arrow to select the data and then click on import.

11. Importing Data Through the Web Cont.  Try the import from web tool with the following websites: http://www.bls.gov/news.release/cpi.t01.htm http://www.bls.gov/news.release/cpi.t01.htm  http://finance.yahoo.com/q/hp?s=YHOO http://finance.yahoo.com/q/hp?s=YHOO

12. Handling Duplicate Values and Creating Histograms  There are times when your data set has many duplicate values and you are interested in the frequency of those values known as a histogram.  Excel has the ability to remove duplicate values on the Data ribbon.  Once you remove these duplicates, you can use the unique values to develop a histogram.

13. Histogram In-Class Activity  In column A, copy the RandBetween(1,10) function in cells A1:A5000.  Copy and paste special those values into the C column.  Remove the duplicates from this new column.  Create a histogram out of the original data using the non-duplicate values and the Countif() function.  Press F9 several times to see how the histogram changes.

14. Data Validation  Excel has a tool that can ensure that the data that is being entered is the correct type of data.  This tool is the Data Validation Tool located on the Data ribbon.  The tool has three tabs:  Settings  Input Message  Error Alert

15. Data Validation Cont.  The Data Validation tool can check to see if the data entered is a:  Whole number  Decimal  List  Date  Time  Certain text length  Custom (which is based on a formula)

16. Data Validation Cont.  With the Data Validation tool, you can set-up a message that tells the individual what type of data they should enter.  The Data Validation tool allows you to also put an error message in case a correct value is not entered.

17. Data Validation Cont.  You have the option to:  Stop the individual before the wrong data is entered,  Provide a warning to the individual about the wrong data, or  Provide information to the individual regarding the wrong data.

18. Different Types of Errors  #DIV/0!—This error alerts you when you have divided by zero.  #N/A—This error alerts you when the information is unavailable.  #NAME?—This error alerts you Excel does not know the name you are using, e.g., =SQRT(dog).

19. Different Types of Errors Cont.  #NULL!—This error indicates that the formula you are using does not have an intersection point.  Most of the time this error occurs because you are missing an operator, e.g., =SUM(A3:A5 A4:B7) vs. =SUM(A3:A5 B3:B5).  #NUM!—This error alerts you to an invalid number, e.g., Sqrt(-100).

20. Different Types of Errors Cont.  #REF!—This error alerts you to an invalid cell reference.  This typically happens when you delete a referenced worksheet in a formula.  #VALUE!—This error alerts you to incorrect data types, a function’s argument is a range when it should be a single value, e.g., =SQRT(A3:A4)

21. Different Types of Errors Cont.  The Iferror() function can handle errors when they come up.  The Iserror() function can check to see if you have an error; it returns true or false.

22. Auditing Toolbar and Formula Auditing  Excel on its Formulas ribbon has a section for formula auditing.  This tool allows you to trace the precedents and dependence of a cell.

23. Auditing Toolbar and Formula Auditing Cont.  It can allow you to toggle between the formulas and the results in a cell.  It can show you how a formula is being evaluated.

24. Circular Reference Errors  When building formulas, you sometimes run into an error known as a circular reference.  This error is alerting you to the fact that the cell you are currently calculating is somehow reliant upon itself causing a circular reference.

25. Circular Reference Errors Cont.  Sometimes you can use circular references as a tool for making a calculation, but typically it is an error you need to handle by fixing the circular reference.