Appendix A. HINTS WHEN USING EXCEL w

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1 Appendix A HINTS WHEN USING EXCEL w This appendix provides hints when using Microsoft Excel. Appendix A includes general features that are useful in all the applications solved with Excel in this book. Other features are illustrated in the context of specific examples, and a list of them is provided at the end of Appendix A for handy reference. You may want to skim this appendix first, then start working some of the problems that use Excel before you come back and review this appendix in more detail. That way you will not be burdened with details that do not make sense to you until you see where and how you need them. For a more detailed description of Excel, consult other books devoted to Excel, such as Larsen (2002). CELL ORGANIZATION The rectangular array of cells is labeled A, B, C, D... across the top, and 1, 2, 3, 4,... down the left-hand side (Fig. A.1). Cell B3 is in the second column (B column) and the third row from the top. (As in linear algebra with matrices, columns go down and rows go across.) CELL CONTENTS You can enter a number, word, or formula into the cell. To enter a number, click on the cell and type the number. Pressing return will move down one cell, pressing tab will move across one cell, to be ready for the next entry. To enter a word, select the cell and type the word. The word can also be preceded by a single quote, which is useful if the Excel is a registered trademark of Microsoft Corporation, Inc. Introduction to Chemical Engineering Computing, by Bruce A. Finlayson Copyright # 2006 John Wiley & Sons, Inc. 229

2 230 APPENDIX A Figure A.1. Cell contents: naming cell, formulas, text. word is actually a number. To enter a formula, select the cell, enter ¼ followed by the formula. The cell can be referenced by its location, for example B1, but it can also be named. To name it, select the cell and enter the name of the variable in the upper lefthand corner of the spreadsheet and then press return or enter. Then to use the value in B1, you can use the variable name temperature rather than B1, as in Figure A.1. The entries in this figure are: B1 is named temperature B3 is: 1 0:01 temperature B5 is: ¼ 1 0:01 temperature (A:1) (A:2) (A:3) FORMAT Under the Format menu bar are several options that make your spreadsheet more readable. With the Format/Cells...you can change the way numbers are displayed, the alignment of them within the cell, and the font properties. You can also set a border around some cells, and change the pattern or color (the Color option is inside the Pattern option). You can even protect the spreadsheet or parts of it so others cannot change it. With the Format/Row option, you can change the height of one or more rows, and you can hide a row. To make it visible again, choose the rows on both sides of the line, and choose unhide. The same options work for columns, and the width of the columns can be changed. You can do this for all rows/columns, for only rows/columns you select, or you can use the scroll bar to change a single row or column by dragging the boundary. The Format/Conditional Formatting option allows you to cause the cell to change color, for example, if a parameter meets certain conditions. This can be used as a red flag (literally!) to highlight mistaken results or mistaken input and provides a form of data validation. COMMENTS You can insert comment boxes on your spreadsheet by selecting Insert/Comment. Type the desired comment and click Return. You can also insert a text box of any desired size. Open the drawing menu, select the textbox symbol in the drawing tools, and use the mouse to draw a rectangle. You can then type inside the rectangle.

3 SPLIT/FREEZING 231 PICTURES, EQUATIONS, WEB LINKS You can insert pictures, equations, and hyperlinks (to web sites), too. Choose Insert/ Picture and choose the picture you want. To enter an equation, Choose Insert/Object and choose Microsoft Equation. You may have to add that feature to your spreadsheet if it was not included during installation. (You need the original CD or ask your System Administrator to install it.) For hyperlinks, simply choose Insert/Hyperlinks and insert the web address. Be sure to try it while connected to the internet to ensure that it works. SELECT COLUMNS FOR CHARTS, REGRESSION, AND PRINTING Put the cursor in the upper-left cell that you would like to select and drag down until the shaded box covers all the columns and rows you want. Note that the columns and rows have to be contiguous, or next to each other. You can do this to two or more contiguous columns or rows. Use this same procedure for selecting the print area. COPY FORMULAS ACROSS AND DOWN THE SPREADSHEET To copy a formula across the spreadsheet, select the cell and put the cursor on the lower right-hand corner of the cell. Drag the cursor to the right. The column entries of formulae are incremented one by one. Suppose the original formula used B2. If the formula is dragged to the right, B2 is changed to C2. If the formula is dragged down, the B2 is changed to B3. If you do not want that to happen, that is you want the formula in all columns to use B2, then use absolute addresses. In the formula, change B2 to $B$2. Options like $B2 and B$2 are also possible. If you select a cell tag in the equation and press F4, it turns into an absolute address. On the Apple Macintosh, selecting the cell tag and pressing command-t does the same thing; if you continue to press it, the tag cycles between B2, $B$2, B$2, $B2, B2,... INSERT ROWS AND COLUMNS Select a row on the left-hand side and choose Insert/Row. A new row is placed above the one you selected. The cells are renumbered, and all the formulas are changed, too, to reflect the new numbering system. Use this same method to insert a column; the new column will appear to the left of the one you have selected. SPLIT/FREEZING You can split the screen into four portions in a 2 2 array. To do this, select the cell that will be in the center, that is, the upper left corner of the lower right rectangle. Then choose Windows/Split. You can later choose Windows/Remove Split if you want. In Figure A.2, the cursor was placed in cell F3 before choosing Windows/Split. Sometimes the Registered trademark of Apple Computer, Inc.

4 232 APPENDIX A spreadsheet is very large, but the parts you want to see are at the beginning and end. Figure A.3 shows a numerical integration of a differential equation, starting from t ¼ 0 (see Appendix F). You are interested in the results at t ¼ 1, but want the heading, too. Place the cursor on the 3 designating row3 and choose Window/Freeze Panes. Then rows 1 and 2 remain visible while you scroll down to row 102, as shown in Figure A.4. ITERATION ON, TOLERANCE Figure A.2. Split window. You can use Goal Seek or Solver to find the roots of a function. You may find that the answer is not as accurate as you would like. (The default parameters are set for business applications, where tenths of a cent do not matter.) To get a more accurate answer, you need to make the tolerance smaller. Choose Tools/Options and click Calculation. On the Macintosh, choose Preferences and click on Calculation. Figure A.5 shows the default values. Change the maximum iterations to 1000 and the maximum change to and close, then run Goal Seek. You can make the same choices in Solver by choosing Options. This is also the place to turn off the Iteration function by unchecking the iteration box. This is sometimes useful when solving a problem in which the formulas are intertwined and the formula in one cell depends on the answer in another cell, which depends on the value in the first cell. In these cases it is convenient to turn off iteration while preparing the formulas in the spreadsheet, and then turn it on once the entire spreadsheet is complete. PASTE Sometimes you want to reproduce part of your spreadsheet in another spreadsheet or in another area of your existing one. You can select the area of the spreadsheet, choose Figure A.3. Window/Freeze Panes, start.

5 PLOT xy SCATTER, EDIT, MULTIPLE CURVES, SURFACE PLOTS 233 Figure A.4. Window/Freeze Panes, after scrolling down. Copy, move to the upper, left-most cell of the new area and choose Paste. Be careful because this will copy all formulas, too. If you want only the values from a spreadsheet, copy the part you want and choose Paste Special; then choose the desired option (such as Value). You can also paste into Word. If you simply use Paste, you can manipulate the spreadsheet inside Word (resize it, change the font, etc.). If you use Paste Special, one option is to paste the spreadsheet as a picture. In that case the whole image is frozen before it is put into Word. PLOT xy SCATTER, EDIT, MULTIPLE CURVES, SURFACE PLOTS Plotting in Excel is easy. Choose the cells you wish to plot, such as columns A and B in Figure A.6. If you want, choose the headings, too, and they will appear in the graph Figure A.5. Iteration and calculation window.

6 234 APPENDIX A Figure A.6. Plot of a single line. (although they can later be changed). Then choose Insert/Chart, choose xy Scatter, and click on the graph style you want. The program takes you through a series of steps in which you can enter a title, label the x and y axes, and so on. Finally, tell the program to place the chart on the graph. To remove the meaningless label Series 1, select it and press Delete. To edit any part of the graph put the cursor on the part and right-click (on the Macintosh use Apple-click). A screen will appear that allows you to make other choices for the graph. To put multiple lines on the graph, select more columns. For example, if you select columns A, B, and C, you can produce Figure A.7. To make a contour plot or 3D view, create the data to be plotted in a rectangular part of the spreadsheet. In Figure A.8, the A column and seventh row are the y and x values, respectively, and the other values are the ones to be plotted. Select B2 F6, choose Figure A.7. Plot of two lines.

7 ARRANGE SPREADSHEET 235 Figure A.8. Data for contour plot. Insert/Chart, and choose Surface. In this case, choose the contour plot picture (you could also choose the 3D view). Follow the Plot Wizard. In step 2, choose the Series tab, and arrange it as shown in the left-hand side of Figure A.9. This allows you to put x and y values along the axes. The rectangular domain will be plotted as a function of the cell numbers or entry numbers, not any values you assigned to each row or column (see Figure A.9). Also, the plot is flipped (note the location in the spreadsheet where the maximum occurs and the location in the plot where it occurs, too.) If you wish to have more contours, after the plot is made, right-click on the legend and set new contour levels. There is no point in having a different increment between the x points or the y points, because the graph is going to be made using constant increments. This is a serious limitation of Excel for scientific plotting. You can make the final result look like Figure A.9. ARRANGE SPREADSHEET To make a professional-looking spreadsheet, it is important to provide documentation for the reader. You can establish different sections, surrounded by boxes (see Figure A.10): Title, your name and date Data Input these are values that the user may change Figure A.9. Contour plot.

8 236 APPENDIX A Figure A.10. Spreadsheet arranged for easy understanding. Parameter Values these are values that the user will not change, but are needed (not shown) Formulas used this defines the problem Results To make the boxes, select the cells to be enclosed, choose Format/Cells/Border, choose Outline, and click OK. In the example above, the equation in cell B12 is ¼ temperature, which gives the same result as ¼ B6. IMPORT AND EXPORT TEXT FILES, ONE COLUMN AT A TIME There are several ways to do this. The first method works when you have a single column to transfer. To export from Excel, select the column of cells, choose Copy, open an application that accepts text files, and choose Paste. To get a single column of numbers into Excel, copy the column in another application, in Excel select one cell, and choose Paste. IMPORT AND EXPORT TEXT FILES, MULTIPLE COLUMNS To export from Excel, select the columns you wish to export, Copy, change to another application file and Paste. To do the reverse operation, copy the text data, open Excel, put the cursor in one cell, and choose Paste. If the original text file had tabs in it (is tab delimited), each entry will go into a different cell. If you do not prepare the text file appropriately, you may get a mess (the whole file put into one cell or one column. If you create several columns in Word using tabs, you can copy the columns and paste them into the spreadsheet and the entries will go into successive cells. EXPORT A TEXT FILE You can export the contents of the spreadsheet to a text file that can be used as the input to another program. This is a nice way to have a user interface for a program that requires

9 MATRICES 237 significant computing capability (beyond what Excel offers). You could put the physical parameters for the case you are studying into the Excel spreadsheet, allowing them to be changed easily. You then export the information and have the other computer program read the text file to get the data. To export the information (the contents of the cells, not the figures from the spreadsheet), choose SaveAs, change the format to a text formats, such as Text(Windows), and save it. It will have.txt appended to the name. If you open that file, name.txt, in a word processor or text editor, you will see the information displayed in exactly the same format as in the spreadsheet. It is not simple to get these numbers into other programs, which have to read the spaces appropriately, and some knowledge of the C computer language may be necessary, but it does make a nice interface for a program that you will use many times. MATLAB w can read such files, for example. TOOLS The power of the Excel program lies in its tools. Goal Seek and Solver were discussed Chapters 2 4, and Data Analysis is discussed in Appendix E. Other useful tools include Tools/Protection (to prevent part or all of the spreadsheet from being changed) and Tools/Flag for Follow Up (to notify you on some future date when you may need to update the spreadsheet). FUNCTIONS Excel comes equipped with many engineering functions. Choose Insert/Functions. Then choose Math & Trig or Engineering to see the functions. A window appears that explains how to use the functions. MATRICES Two of the functions under Math & Trig are MINVERSE and MMULT. These functions have the obvious use. The inverse function, of course, must act on a square matrix, and creates a square matrix. To use it, first create the matrix, as illustrated in cells A1:C3 of Figure A.11. Figure A.11. Matrix inversion and multiplication.

10 238 APPENDIX A Then in cell A6 type ¼MINVERSE(A1:C3). You can also insert the A1:C3 by selecting the cells. Click on cell A6, press the shift key, and select the other corner of the matrix, C8. Press F2, the Ctrl-Shift-Enter. The inverse appears in A6:C8. The matrix multiplication is illustrated in Figure A.11 by multiplying these two matrices together; the result should be the identity matrix. Click on cell A11, type ¼MMULT(A1:C3,A6:C8). Click on cell A11, press the shift key, and select the other corner of the matrix, C13. Press F2, the Ctrl-Shift-Enter. The matrix multiplication appears in A11:C13. Indeed it is the identity matrix. EXCEL HELP When you are truly stuck, try the Help/Search Excel Help. You can type in a question and it will alert you to several possible answers related to your question. This usually leads you to the answer you want. APPLICATIONS OF EXCEL Listed here are applications of Excel using specific tools so you can find them easily.. Equations of state, Chapter 2, p. 8.. Vapor liquid equilibrium, Chapter 3, p Chemical reaction equilibrium, Chapter 4, p Process simulation using Excel, simple mass balance, Chapter 5, p. 58, 60, 62.. Process simulation using Excel, including chemical reaction equilibrium, Chapter 5, p Process simulation using Excel, including phase equilibrium, Chapter 5, p Continuous stirred-tank reactor, Chapter 8, p Straight line curve fit using Excel, Appendix E, p Polynomial regression using Excel, Appendix E, p Multiple regression using Excel, Appendix E, p Nonlinear regression using Excel, Appendix E, p Finite difference method for boundary value problems, Appendix F, p Finite difference method for elliptic problems, Appendix F, p. 321.