3131 Spreadsheets Practical 1€¦ · Web viewIn cell C1 type the word Total making sure it appears in bold and italic and 12pt font. There are also standard, frequently used, formats

CSC931 COMPUTING SCIENCE I SEPTEMBER 30TH/OCTOBER 1ST 2010SPREADSHEETS PRACTICAL 1

CSC931 – Autumn 2010Spreadsheets Practical 1

LEARNING OUTCOMESBy the end of this practical you should be able to construct spreadsheets to solve simple problems. You should: be able to enter data in a simple spreadsheet be able to format cells to reflect different data types understand the difference between data and formulas be able to sort a list of data using different criteria be able to use simple functions in spreadsheets be able to define names for cells in spreadsheets

SUPPORTING DOCUMENTATIONAs usual, see the recommended course texts, and the Library and IT Skills course on WebCT. Lastly, the Excel Help system can be surprisingly helpful … try it!

Remember: to run the registration program! Saving: Don't forget: if you plan to work on your documents elsewhere in a previous version of the Office Suite, then you must save them in an appropriate format. Please ask if you don't know what this means.In your own time: if you are unfamilair with Excel, you should do the exercise again in your own time to get more familiar. If you already know Excel, why not try using an Excel template to manage your personal finances?

SPREADSHEET BASICS

To launch Excel double click the shortcut on the desktop You will be presented with a new workbook entitled “Book 1”. Note the features below:

DEPARTMENT OF COMPUTING SCIENCE & MATHEMATICS PAGE 1 OF 15

Active Cell Address

Input line

Active Cell

CellsStatus bar


Entering Data To enter something in a cell you simply click on it and start typing. With Excel you can enter three main types of data into a cell:

labels (or text) numbers

formulas

LabelsA label is text that you input to make your spreadsheet more readable

Click on cell A1 and type in Banana Sales in Stirling. For all Excel input you must press Enter to let the program know

you’re finished editing that cell (for now).

You will see that what you are typing is shown on the input line. What you typed in should be displayed on the face of the workbook too.

Look at the face of the workbook. It probably looks as though this label extends across several cells. Don’t be misled. It doesn't. If you look at the input line Excel shows you what is contained in the active cell (i.e. the one that is highlighted). Cell A1 contains the whole label but if you click on cell B1, you will see from the input line that this cell is empty.

Numbers Move to cell A3 and type 42.

That part is simple!

FormulasTo tell Excel that you are entering a formula you must first type an equals sign (=).

Move to cell A7 and type in the formula =29*2.

The value 58 appears on the face of the workbook. But note that the input line shows the contents of the cell as =29*2.

Excel can also perform calculations using other cells as references. For example:


NB: It is important that you understand the difference between what is contained in a cell and what is shown on the face of the workbook. This is true both for formatting (i.e. labels which are really in just one cell, but look bigger), and for the difference between formulas and their results (see below).


Move to cell A9 and type in =A3*A7. The answer 2436 should appear on the face of the workbook (because 42*58 = 2436). (If you omitted the = sign, the first thing Excel sees is a letter so it treats what you are typing as a label). Remember the cell contains the formula =A3*A7 and not the value 2436. Alter the contents of cell A3 to 44. You will see that the value shown at cell A9 automatically changes to 2552. This is an example of recalculation of formula - when the contents of a cell is changed all cells referring to this cell in their formulas (either directly or through other formulas) are recalculated. This is the main reason why spreadsheets are so useful.

Editing Cell contentsThe simplest way to edit the contents of a cell is to select the cell you want to change, re-type the data you want and press Enter. This simply overwrites the previous contents of the cell.

In A1 type Hallo World.

The string “Hallo World” has replaced the previous contents of A1.

Sometimes, you just want to slightly alter the contents of the cell.

Double click on A1

The contents of this cell are ready for editing.

Change the “a” to an “e”.


Hint: You don’t need to use capital letters – Excel converts them automatically.

Another useful tip is that you don’t even need to type cell references at all! If you click on a cell while typing a formula Excel puts that reference in for you. Try it:Move to cell A9 (there is no need to erase the current cell contents): Type the = sign and then click on cell A3. You will see on the input line that Excel generates a cell reference for you. Type * (this will automatically be entered in cell A9) Now click on A7. Note again that the cell reference is generated for you, press Enter or click on the tick mark next to the input line and the required formula is entered into cell A9. This method of entering formulas avoids errors in reading cell references and is especially useful when dealing with cell ranges.


The corrected label “Hello World” should now appear on the face of the spreadsheet. Note that you didn’t have to type the whole thing again.You can do all this in the input box too. When you select a cell its contents appear in the input box, and you can edit it there. As above, press Enter to accept the change. You can also click on the little tick which will appear to the left of the input box.

Selecting a Group of CellsSometimes you may want to perform the same operation on each one of a group of cells - for example you may want to delete a chunk of data. Rather than dealing with each cell individually it is possible to select a group of cells using the mouse and then perform the same operation on all of them simultaneously. For example we can delete the cells from A1 to C9 thus:

Select all the cells from A1 to C9. (Don’t let go of the mouse button in between or else you end up moving the contents of the first cell to another position.)

Press the Delete key

All the contents of the cells in the block should now have disappeared.

Click Undo (the usual buttons are at the very top of the window).All the contents of the cells in the block should now be restored.

Formatting CellsWe now want to improve the readability of the spreadsheet. There are various ways to change the formatting.

First, text can be formatted in the same ways as you would format it using Microsoft Word using the Font panel in the Home tab:

In cell C1 type the word Total making sure it appears in bold and italic and 12pt font.

There are also standard, frequently used, formats for numbers including currency and percentages for which there are speed buttons on the Number panel. We’ll use these to format cells B3 and B4:

Type the numbers 1234, 12, and 22 into cells B2, B3, and B4 respectively.

Click on B3



Click on the Currency button Repeat this process for cell B4

Have a look at the other predefined formats in the Format menu within the Number panel. These might be useful for later exercises …Remember to save your work in a sensible place at regular intervals



STUDENT MARKS EXAMPLE

Copy the folder Excel Practical 1 from the Groups\CSC931\ Folder into your own CSC931 folder.

Open (your own copy of) the file students

You should be presented with a spreadsheet containing a list of 30 student names along with associated marks for 2 assignments and an exam. You’re going to add some formatting and some formulas to present the student results.

Insert a new row along the top of your data and type in the following column headings:

Surname Initials

Ass 1 Ass 2 Exam Total %

Now we want to sort the data: Select the data to sort (i.e. everything except for the column

headings and the first column). Select the Sort & Filter from the Editing panel in the Home tab.

From the drop down menu, select Custom Sort... Select Add Level to add an additional level of sorting for Initials.

Fill in the dialog as follows.

Click OK


In Office 2007 Excel files have the extension .xlsx, but Windows generally hides this from you. Files in Office 2003 format have the extension .xls.

When you click the “My data has headers” radio button Excel detects the column headings you input earlier. By clicking on the down arrow next to each sort by criteria you can choose which column you wish to sort on. Note that you can choose more than one criterion. In this example we want to sort by Surname first then by Initial.


Your data should now be sorted alphabetically. You need to be sure to select all columns when you sort because otherwise the names get associated with the wrong marks.

Insert a new column before the Surname column.We want to number the students from 1 to 30, but we don’t want to have to type those numbers in ourselves. Excel has a shortcut. Click in cell A2 and type in the value 1. Click in cell A3 and type in the value 2. Move the mouse to the bottom right of cell A3 - when the mouse

pointer turns into a black cross click the mouse and drag it down until the labelling shows 30. Let the mouse button go. This is called “filling”. You can do it with formulas too, as you will see shortly.

Next we want to create the total column. For the first student (should be Aitken): In the total column, enter a

formula to add together the three marks in D2, E2 and F2. Now fill this formula down for all students.

Clever! When you use a cell reference, e.g. D2, the default is to use Relative Addressing. For a single formula, the type of addressing isn’t important, but when you copy formulas with relative addressing the references they use change in relation to where they are being moved.

Look at the formulas in column G, the total column. You typed the formula in G2, but notice that in each subsequent row, Excel has filled in a formula with different row numbers. This is exactly what is required here – without relative addressing we would have had the total for Aitken in all the rows.

Next we want to calculate this mark as a percentage. Before we can do this we need to know the total marks possible.

In A36 put the text “Total Marks Available” and in G36 put the number 130.

We now have all the information we need:

Go back to the first student (should be in row 2). In the % column (column H) type in =G2/G36

(G2 is the Total for the first student, G36 is the total possible marks)


Filling can also be achieved using the menu Fill – Right within the Editing Panel, but you have to select the target area first in that case.


Format this to be a percentage with one decimal place using the Format list in the Number panel.

Fill this formula down.

Yikes! What has happened?

This time, the cell reference G36 shouldn’t use Relative Addressing. Here we always want to use the same cell in the each of the formulas i.e. G36. What happened in this example is that the formula changed relatively so that while H2 contained =G2/G36, H3 contained =G2/G37 and so on. Since G37 contains nothing we get a divide by zero error. To get over this problem we use absolute addressing. In this way when we copy a formula the references do not change no matter where we copy it to in the spreadsheet.

Amend the formula to =G2/$G$36. The dollar signs tell Excel to fix the cell reference in both the column and the row.

Fill this new formula down to the other cells

Another way to ensure absolute addressing is to define a name for the cell and then use the name in the formula e.g. If we had defined G36 as Total_Marks we could have used =G2/Total_Marks in the formula. Names will be used in the next example.

A third style of addressing is Mixed addressing. More on that next time.

Tidy up the spreadsheet a little.i.e. make the headings bold, and adjust the widths of the columns to fit the data.

You should end up with something like:



Using Simple FunctionsNow we can add some averages at the bottom of each column: Click on D32 Type in =AVERAGE( Select D2 to D31 (a dotted line should appear around your selection) Type in ) and press Enter Now copy this across for the other columns (Ass 2, Exam, Total, %).Remember to format the cell in the % column.

Do the same to calculate the Min mark for each column in row 33, and the Max mark for each column in row 34.

Add some suitable labels in column A.

CONCRETE SLAB

Also in the Excel Practical 1 folder you will find a file called concrete – open it in Excel. In this exercise you must imagine that you are running a small builders' business laying poured concrete slabs (suitable for building a house on). You are required to construct a spreadsheet that can be used for making quotations to customers over the telephone. The dynamic inputs are the width, height and thickness of the concrete slab – the spreadsheet must calculate a job costing (i.e. how much the customer will pay).


AVERAGE is just one of the many built in functions available in Excel. For information on other functions refer to Excel help. Briefly, though, the deal is that you can click on the button marked fx and Excel will offer you a range of handy formulas. Or you can use a function from the pop up function box which appears where the name box usually is. Or you can just type them in, as we just did.


THE INFORMATION YOU NEED

For Material Costs:For each cubic metre of concrete you need:

8 bags of cement0.5 cubic metres of sand1 cubic metre of gravel

1 bag of cement costs £8Each tonne of sand costs £16Each tonne of gravel costs £18

Each cubic metre of sand weighs 1.4 tonnesEach cubic metre of gravel weighs 1.3 tonnes

For each job (no matter how large or small), we assume that 0.5 bags of cement, 0.25 tonnes of gravel and 0.25 tonnes of sand are wasted.

For Labour CostsWe assume that one man can lay 5 cubic metres of concrete per hour. Rate of pay is £15/hour.

Profit and TaxWe want to make a 50% profit above our costs. VAT is set at 17.5%. (When you type in percentages they need to be entered as decimal fractions i.e. 0.5 and 0.175.)

Initial DimensionsWe will initially set up the spreadsheet to calculate an area of cement with the following dimensions:

Height: 0.15mDepth: 6mWidth: 3m

So where do we start? The spreadsheet will use lots of absolute addressing, so to save typing all those dollar signs let’s define some names for the values.

Select the Formula tab. Select B2 and click Define Name in the Defined Names panel.Excel is smart. It guesses that the name might be either above or to the left of the cell selected, so it already has height as a suggested name. Click OK. Name B3 Depth and name B4 Width.

Names can be used in a formula. Make a formula for the volume:



Type in =Height*Depth*WidthRemember you can include a cell reference (even a name) by clicking on the cell while typing the formula.

Name the rest of the cells in column B as follows. Sometimes Excel will guess right, and sometimes you’ll need to type the name yourself.

Cell Name to Define to Cell Name to Define to

B5 Volume B18 Weight_GravelB8 Cost_Cement B20 Wastage_CementB9 Cost_Sand B21 Wastage_SandB10 Cost_Gravel B22 Wastage_GravelB13 Amount_Cement B25 Volume_ManB14 Amount_Sand B26 Man_HourB15 Amount_Gravel B27 ProfitB17 Weight_Sand B28 VAT

THE CALCULATIONS....Remember, the whole point of the exercise is to be able to work out how much to charge the customer. In order to do that we need to first work out how much cement, sand and gravel we need, how much that will cost, and how much the labour will be. Note that some useful labels for the formulas we need have been entered in column D.

Cement:How many bags of cement do we need for this job?We know that to make 1 cubic metre of concrete we need 8 bags of cement, therefore to make x cubic metres of concrete we need x*8 bags of cement (where x is the volume of concrete). We have already worked out the volume of concrete we need - so we can use this in our calculation.

First we need to calculate the amount of cement we need in m3:=Volume*Amount_Cement

(Where Volume and Amount_Cement are names you have defined for cells B5 and B13)

But that’s not quite right – remember we also assume that a certain amount of cement is wasted on each job. 0.5 bags to be exact. So add this into the calculation:



Adjust your formula to read =(Volume*Amount_Cement)+Wastage_Cement

Remember, we use formulas and cell referencing here rather than just typing in 0.5. Why? What if you get someone new in the job who wastes more than 0.5 bags? Or someone who wastes less? With formulas, all we have to change is the cell Wastage_Cement; all the formulas stay the same.

Sand:This is slightly trickier. First we need to calculate the amount of sand we need in m3:

=Volume*Amount_Sand

We need to then convert this into tonnes. (We know that sand weighs 1.4 tonnes per m3)

= (Volume*Amount_Sand)*Weight_Sand

Then add the wastage of sand per job= ((Volume*Amount_Sand)*Weight_Sand) + Wastage_Sand

In cell E3 enter the formula =((Volume*Amount_Sand)*Weight_Sand)+Wastage_Sand

Gravel:This is worked out in the same way as sand - try it for yourself. Then define names for these three new cells and format them to make it look pretty!

OK So Now the Costs...

Multiply the quantities you have just calculated by the costs that you entered before.

A quick way to calculate the total materials cost is to highlight cells F2 to F5 then click the AutoSum button. You can find this on the Function Library panel on the Formulas tab. This adds the values in cells F2..F4 and places the answer in F5. (In fact, if you click on the arrow to the right of the Sigma symbol on the button you will see some other useful functions.)

ON YOUR OWN....Calculate the labour costs - you know how much concrete has to be laid, you know how much a man can lay in 1 hour and how much he gets paid per hour - you work out the rest.



Make a subtotal (Sub-Total-1) adding the materials cost and the labour costs.

Work out how much the profit would be (using the percentage profit in B27).

Make another subtotal (Sub-Total-2) of the previous sub-total and the profit.

Now calculate the VAT (using the VAT rate from B28).

Now add the previous subtotal and the VAT to get the final costs (at last!).

Your spreadsheet should now look like the following screenshot (without the lovely formatting):

Because all the formulas are related to each other you can change any of the values in column B and the rest of the spreadsheet will automatically be re-calculated using the new values. In this way not only can you calculate the costs for any size of job, but if you want to put your profit margin up or down, or if the cost of sand increases the spreadsheet will automatically re-calculate using the new values. Try it!



CheckpointCheckpoint: Show a demonstrator your students marks file, complete with averages, max and min, and data sorted by student name. Then show them your concrete slab example with completed calculations of the cost of making a concrete slab.Make sure you are marked as having reached the checkpoint.

Checkpoint

Don’t stop just yet!

FORMATTING THE CELLSAs you can see in the example above, you can customise your own format. We’ll do this for B2 so that it looks like 0.15 bananas:

Click on B2 Select the Dialog Box Launcher

in the Number panel Click on the Number tab on the

dialog box that appears Select Custom in the left hand

scroll window Enter into the Type box 0.00

“bananas” as shown (the quote marks are necessary). Note that a sample of the finished formatting is shown in the Sample area. Using 0.00 tells Excel to always show two decimal places for your number.

It shouldn’t be hard to think of other custom types you might want to use: student reg. number, class name, practical and exam marks are all examples from the educational field.

Now you’ve completed the calculations for the concrete slab, format the cells so that they look like below.


NB: If you click on the cell and look at the input line you will see that it only contains 0.15 although on the face of the spreadsheet it looks like 0.15 bananas. This is NOT the same as typing “0.15 bananas” directly into a cell. Excel regards anything with a letter in it as a label - and you cannot use labels in formulas.


You can use the buttons on the Number panel to quickly format cells as currency and percentages.

Use the custom style for numbers to add “tonnes”, “bags”, “m3” after a value. Remember the difference between text that appears as formatting and text that appears because you type it in. You can do calculations on one but not the other!

ON YOUR OWNThe cost of materials is based on fractional quantities. For example, we need 22.1 bags of cement. But we can’t buy 0.1 of a bag of cement. To be more accurate the figures in column E should be rounded up to the nearest whole number. Find a function to do that for you.

NEXT TIMEAll that was perhaps quite challenging.

But you can see that once you’ve done the design/donkeywork of setting the spreadsheet up, life becomes a lot easier if you want to try out various figures. Next time, we’ll do charts and graphs and some more formulas with absolute, relative, and mixed addressing.


Documents

3131 Spreadsheets Practical 1€¦ · Web viewIn cell C1 type the word Total making sure it appears in bold and italic and 12pt font. There are also standard, frequently used, formats