Chapter 4- Excel Formulas
Formulas
A
worksheet is a set of cells aligned in rows and columns. The cell content can
be a statement containing a text message, a number, or a date. Dates are a
special case. Although you see a date, the application stores the information
as a number. It counts the days since
In
Column A Row 1: (Cell A1) the content of A1 is a number with the value 3
In
Column B Row 1: (Cell B1) the content of B1 is a number with the value 5
In
Column A Row 2: (Cell A2) the content of A2 is a label “Text
Message”
In
Column B Row 2: (Cell B2) the content of B2 is a number, 37333, displayed as a
date.
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Column A |
Column B |
Column C |
Column D |
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Row 1 |
3 |
5 |
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Row 2 |
Text Message |
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The
cell content can also be a formula. A formula asks a question and tells Excel to
display the answer to that question. A formula always starts with an = sign.
Think of a formula as “What is?”
followed by a question. A cell containing a formula is like a flashcard; the
cell displays the result of calculating the formula. The formula appears in the
formula bar above the worksheet.
If
you type a cell name in a formula, this is called a cell reference. The formula
uses the value of the referenced cell to calculate its result. For example, if
you type =A1+5 as a formula in cell C1, Excel will look into cell A1, then
calculate the formula after converting the A1 cell reference into the value
stored in A1. In this case the value is 3, and Excel will answer the question, what is 3+5? The answer is 8, which will be displayed in cell C1.
When you enter these statements or formulas in cell C1, here is what will be displayed:
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These statements in cell C1 |
Display this in cell C1 |
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These formulas in cell C1 |
Display this in cell C1 |
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5+3 |
5+3 |
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=5+3 |
8 |
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B1 + 3 |
B1 + 3 |
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=B1 + 3 |
8 |
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A1+B1 |
A1+B1 |
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=A1+B1 |
8 |
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SUM(A1:B1) |
SUM(A1:B1) |
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=SUM(A1:B1) |
8 |
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5+B1 |
5+B1 |
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=5+B1 |
10 |
The =SUM(A1:B1) formula works by referencing a rectangle, called a range. A range's shape is described by the two cell addresses in opposite corners. For example the range (A1:C2) would include the cells A1, B1, C1, A2, B2, and C2. The Sum instruction tells Excel to add the total of all the cells in the range. You can create Summation formulas automatically with an icon (S) found on the Standard toolbar. Summation is normally used to find the total of a row, column, or range of cells, not for simple addition of two cells. If you create a formula by clicking the Summation icon instead of the = sign, it wastes computer power and memory.
Example of ranges: B3:C4, E2:E4, C6:E7
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A |
B |
C |
D |
E |
F |
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1 |
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2 |
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3 |
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4 |
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5 |
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6 |
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7 |
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8 |
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Displaying Formulas: Sometimes you may want to
display the actual formulas, instead of their results. You can highlight each
individual cell and its formula will be displayed in the formula box located
above the worksheet area. To view all of the cells as formulas, press Control
and ~ (tilde). The tilde key is in the upper left corner of the keyboard. Or,
use the Tools menu under Options. There is a checkbox on the View tab where you
can reset the worksheet to display formulas. You can also turn the gridlines on
and off from this location.
Copying formulas: When a formula is copied, Excel automatically changes the row number in any cell references if the formula is copied into a different row. It automatically changes the column letters in any cell references if the formula is copied into a different column. The adjustment is equal to the number of rows or columns between the copied-into cell and the copied-from cell. In the examples given in the tables below, the formula in the source cell C4 was copied to cells E4 (increased column references by 2), C6 (increased row references by 2) and E6 (increased both row and column references by 2).
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C |
D |
E |
Comment |
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4 |
=
A1+B2+C3 |
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=
C1+D2+E3 |
Letters
change when you copy a formula into a different column. Numbers change when
you copy a formula into a different row. |
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5 |
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6 |
=
A3+B4+C5 |
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=
C3+D4+E5 |
Cell references like those in the table above are called
“relative (dynamic) cell references.” You can add dollar signs to
formulas to control the way Excel changes cell references when it copies a
formula. Adding a
dollar sign in a cell reference formula means: Don't change the next part of
this cell reference when copying this formula. When a
formula containing a dollar sign is copied to another cell, the part of the
cell reference preceded by the $ will not change.
Cell references with dollar signs in front of just the number, or in front of just the letter, are called “Mixed Cell References.” Use a mixed cell reference in a formula when you want to create a set of formulas that will always refer to either one specific row: A$1, or one specific column: $B2. If the formula should always use the same cell reference, add two dollar signs: $C$3. This is called an “Absolute Cell Reference.”
You
can combine absolute, mixed, and relative cell references in a single formula.
The dollar sign does not change the resulting value of the formula in any way.
For example, both = A1+B2 and = $A$1 + $B$2 display exactly the same output.
In
the following table, the formula in cell C4 was copied into other cells.
Observe which row and column numbers changed and note the effect of the dollar
signs.
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C |
D |
E |
Comment |
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4 |
=
A$1+$B2 |
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=
C$1+$B2 |
Notice
that only the A and the 2 (in cell C4) change. Because of the $ symbol, the
others don’t change. |
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5 |
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6 |
=
A$1+$B4 |
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=
C$1+$B4 |
One
use for an absolute reference is to divide many numbers by the same constant.
First set up a constant in a cell. Then enter a formula into another cell using
an absolute cell reference in the formula. The formula can be copied and the
reference to the cell containing the constant value is unchanged. Changes to
the cell containing the constant will cause the formulas that refer to this
cell to recalculate their values.
Some common
error messages: Error messages usually
start with a Pound sign (#).
##### If you see rail road tracks, your column is too
narrow. Solution - widen the column.
#DIV/O! You are dividing by an empty cell or
zero. Solution - fix the formula’s denominator.
#REF! Your formula refers to a cell that no longer exists,
due to a change in the worksheet.
#NAME? Your formula contains text that
Excel doesn’t recognize. This could have many causes. Usually it’s
a typo or missing punctuation in a formula, like forgetting the = sign.
Circular A formula can not reference
the cell it is located in; this will generate an error message. You will see Circular followed
by a cell reference in the area below the worksheet.
#N/A You’ll see this if a Lookup Table
couldn’t find a match to the text in the search input cell.
Formulas
using multiple worksheets: You can write formulas that refer to cells in other
worksheets by including the worksheet name in the cell address. For example, if
you typed =Sheet2!C4 in sheet 1, cell A3, that cell
would display the contents of cell C4 in sheet 2. If the contents
of sheet 2 cell C4 was a formula, you would see the results of the
formula, not a formula.
Order
of operations: If a formula contains multiple calculations, Excel calculates the
parts of the formula in this order: calculations in parentheses, then
percentages, then exponentiation, then multiplication and division, then
addition and subtraction, always moving from left to right. Use parentheses to
force Excel to do the calculations in the order you want. For example = 3+4*2
will display 11, since Excel would do the multiplication first, while = (3+4)*2
will display 14.
Some examples of commonly used formulas are given below. There is no one right way to write a formula; getting the correct result is what matters. Spaces are not necessary in the formulas, but they are included below to allow for ease of understanding.
This
Table is used with the Sample Formulas below:
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A |
B |
C |
D |
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1 |
25 |
28 |
95 |
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2 |
42 |
91 |
14 |
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3 |
3 |
4 |
5 |
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SAMPLE FORMULAS:
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Type of Equation: |
Entered in Cell D3: |
Result Displayed in D3: |
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Addition of Two Cells |
= A2 + B3 |
46 |
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Addition of a Constant |
= B1 + 25 |
53 |
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Addition of a Row of Cells |
= SUM (A1:C1) |
148 |
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Addition of a Column of
Cells |
= SUM (B1:B3) |
123 |
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Addition of a |
= SUM (B1:C3) |
237 |
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Addition of Scattered Cells |
= SUM (A2,B1,C3) |
75 |
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Subtraction of a Constant |
= C1 – 10 |
85 |
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Subtraction of a Cell |
= B2 – B1 |
63 |
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Multiplication by a
Constant |
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