C4-1. What Excel is. Creating a pro Fit-Compatible Datafile. We shall use as an example the data that is contained in the file Hooke s Law Data.

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1 Appendix 4 Using Excel Excel, a program referred to in a number of guidesheets in this manual, is useful in nearly every experiment. Five aspects of the program will be dealt with here: how to create a file with Excel that profit can read, how to create a data worksheet, how to enter formulae and functions into an Excel worksheet, how to copy a snapshot of a worksheet to paste into a Word document, and how to graph data. What Excel is Excel is a spreadsheet program that supports mathematical operations on contents of cells. With it one can analyze data simply and quickly. Excel runs on any Mac or Windows PC. To run Excel on the computers in the physics lab do the following: 1 Log into your account on FISSURE, ➁ Inside any experiment folder find and double-click the Excel alias. The Excel original is located inside Macintosh HD >> Other Applications >> Microsoft Office 98. When the program first opens it displays a blank worksheet called Worksheet 1. The first cell will be selected automatically as shown in Figure 1. Figure 1. To start filling in a worksheet when the first cell is selected, simply commence typing. To move one cell right press the <TAB> key. To move one cell down press the <RETURN> key. The arrow keys can also be used for this purpose. One of the most useful application of Excel is to prepare a file that profit can read. If you know how to do this already, skip one page to the section How to Create a Data Worksheet. Creating a pro Fit-Compatible Datafile We shall use as an example the data that is contained in the file Hooke s Law Data. Begin Worksheet 1 by typing in the first cell (A1) as shown in Figure 1. A profit-compatible datafile must consist of four columns only. These columns contain X, X, Y and Y. Therefore, Worksheet 1 must also consist of four columns A, B, C, and D, containing only numerical data. In C4-1

2 addition, the file must not contain alphabetical data anywhere within it. Figures 2a and 2b show how to move the pointer around on the worksheet using the <TAB> key, the <RETURN> key, the cursor control keys, and the mouse. (a) (b) Figure 2. Entering numbers from the file Hooke s Law Data. Columns A, B, C and D will contain the values X, X, Y, Y. In (a) data is entered moving left to right along a row. In (b) data is entered moving down a column. A cell may be selected directly by positioning the pointer (in the form of a Greek cross) over the cell and then clicking once. The cursor control keys may also be used to move between cells. Type carefully. Continue in this way until you have entered all the numbers. The resulting worksheet will resemble Figure 3. Figure 3. Worksheet 1. Having completed your worksheet do the following: 1 Choose Save As from the File Menu. A dialog box resembling Figure 4 on the next page will appear. ➁ Confirm that your user name appears at the top of the box. If it does not, click on the Drive button until it appears. ➂ Type in a name for your sheet in the space provided. ➃ Click on the Text button. This is important, as your file must be Text or else pro Fit will be unable to read it. 5 Click Save. C4-2

3 Figure 4. The Save As dialog box. The file must be saved as Text or pro Fit will be unable to read it. The file is saved with a <TAB> character between each field (along a row) and a <RETURN> character between each record (at the end of a row). Having saved your file you may now quit Excel and double click pro Fit. Once pro Fit is running, the file may be opened in the usual way. How to Create a Data Worksheet A data worksheet is much the same as a profit-compatible datafile except it has no restrictions. A data worksheet may contain text as well as numbers and may consist, within limits, of any number of rows and columns. How to Enter Formulae and Functions You can enter formulae and functions into a data worksheet very easily. Consider again Worksheet 1 as shown in Figure 5. Suppose you require an average of all the X values. The formula for average can be entered into cell A6. To enter this formula type =AVERAGE(A1:A5) and press the <ENTER> key. Don t forget the equals sign; it tells Excel that what follows is a formula.the formula =AVERAGE(A1:A5) means take the average of cells A1 through A5. Table 1 lists some of the more useful functions. The many other functions and features of Excel can be discovered by selecting Help from the Menu when Excel is running. Table 1.Some Useful Excel Functions COUNT(numbers-1, numbers-2, ) EXP(number) LN(number) LOG10(number) MAX(numbers-1, numbers-2, ) MIN(numbers-1, numbers-2, ) PI() ROUND(number, number-of-digits) SIN(number) SQRT(number) STDEV(numbers-1, numbers-2, ) SUM(numbers-1, numbers-2, ) TAN(number) C4-3

4 Figure 5. Worksheet 1 with the formula =AVERAGE(A1:A5) entered in cell A6. The formula also appears in the formula bar at the top of the screen. Copying and Pasting a Snapshot of the Worksheet From time to time and in various experiments you will asked to provide proof of your work in the form of a printout of your worksheet on the laserwriter printer. This is best done from within a Microsoft Word document. To do this a snapshot of the worksheet must first be copied to the clipboard from within Excel. Do the following: 1 Identify the section of your Excel worksheet you wish to copy. ➁ Click on the cell in the upper left corner of the identified area. Scroll to the bottom right cell. Place the pointer over the bottom right cell and with the <SHIFT> key held down click the mouse button once. The whole sheet should thus be selected. ➂ With the <SHIFT> key held down, choose Copy Picture from the Edit Menu. This copies the selected area to the clipboard. ➃ Quit Excel and open Word. 1 ➄ When Word is running, press the <RETURN> key once or twice to move down the page one or two lines. Then choose Paste from the Edit Menu. A picture of the worksheet should appear in your document. You may then print this document or Save it to your workspace on FISSURE in the usual way. Graphing Graphing in Excel is not difficult, although it does require learning the program s business oriented terminology. Let us suppose you wish to produce a line graph of a file of data in text form (this description applies to any file in text format). Do the following: 1 Run Excel and from within the program Open the text file of your choice. For example this file might be Ohm s Law Data. 1 As described in footnote 2 if you are running a G3 machine you don t have to quit one program before running another. You may go to the finder and then simply run the second program. System 8.1 supports the running of several programs concurrently. C4-4

5 ➁ Delete any columns (or rows) on the sheet in which error data is stored. Excel does not support the display of error bars! ➂ Select the data to be graphed and then choose Copy from the Edit Menu. The data area should be darkened and a marque should move around this area (Figure 6). ➃ Choose New from the File Menu. ➄ From the dialog box that results choose Chart and click OK. The Chart window should appear ready for you to perform a Paste Special. Figure 6. The student has selected the data to be graphed on the worksheet, chosen New from the File menu and is in the process of choosing Chart from the dialog box. For this process to work you must choose Paste Special from the Edit Menu. A dialog box as is shown in Figure 7 will then appear. Pay particular attention to the following steps: 1 On the Paste Special dialog box click on the Columns button. (In your case if your data is arranged in rows as in the experiment Weather click on the Rows button.) ➁ Click in the box Categories (X Labels) in First Column. This is consistent with data being arranged in pairs (X, Y). ➂ Click in the box Series Names in First Row ONLY if you have entered the names of the columns on your sheet. (This enables the names to appear on the subsequent graph.) In this example the names are not present so this box is not clicked. ➃ Then click OK. A bar graph will then be plotted (not shown here). C4-5

6 Figure 7. The Paste Special dialog box. A bar graph is plotted by default and this is not usually the graph that is wanted in physics. If you choose Line from the Gallery Menu a window like Figure 8 will appear. Choose whichever graph type you wish and then click OK. The choice shown in Figure 8 results in the graph shown in Figure 9. This concludes the tutorial on the use of Excel. Good luck! Figure 8. Choices available under the Gallery Menu. Figure 9. The final product. A line graph produced from the file Ohm s Law Data. C4-6