[vip_students] Excel Tutorial:Lesson 24,Understanding Formulas
- From: "NCBI Technical Support" <paul.traynor@xxxxxxx>
- To: <vip_students@xxxxxxxxxxxxx>
- Date: Mon, 7 May 2007 17:35:17 +0100
Hi All,
In this lesson we begin the hard work. Sorry but there is no easy way around
it now we start to deal with the heavy parts of excel. I want you to study
this lesson carefully and think about it. Some of you may know it but I am
sure there will be others who have only come across this for the first
time.
Topic: Understanding Formulas
Introduction. The purpose of Excel is to perform calculations on the data
you entered in your worksheet. You must use formulas to perform these
calculations. A formula is a mathematical expression that is composed of
numeric values, cell references, functions, and operators. The data that is
produced by a formula changes when other values used or referenced in the
formula change. In Excel, all formulas begin with an equal sign. The equal
sign directs Excel to treat the data as a formula rather than as a constant
value.
Formula Terms. In order to use formulas effectively, you should be familiar
with the following terms:
Constant Value. A constant value is any data you type into a cell. This
includes text and numeric figures such as dates, times, currency, or
percentages. This type of data does not change unless you manually edit it.
You should only use constant values in formulas when the value will not
change frequently. For example, if you want to calculate the sales tax,
enter the tax rate in the formula only when you know the tax rate will not
change often. If the tax rate changes frequently, then enter the rate into a
cell and use the cell reference in the formula.
Function. A function is a pre-defined formula. Excel offers numerous
functions to help you analyze your data. You will learn more about functions
later in this lesson.
Operators. Operators are symbols that represent the type of calculation you
want to perform. The following are common arithmetic operators:
Plus Sign (+): Use the plus sign (+) to indicate addition.
Minus Sign (-): Use the minus sign (-) to indicate subtraction. (JFW reads
the minus sign as "dash.")
Asterisk (*): Use the asterisk (*) to indicate multiplication. (JFW reads
the asterisk as "star.")
Forward Slash (/): Use the forward slash (/) to indicate division.
Caret (^): Use the caret (^) to indicate exponentiation.
Percent Sign (%): Use the percent sign (%) to indicate percentage.
You can use these comparison operators to establish a relationship between
the operands: Equal Sign (=), Greater Than (>), Less Than (<), Greater Than
or Equal To (>=), Less Than or Equal to (<=), and Not Equal To (<>).
Operand. Operands are the elements to be calculated. An operand can be a
constant value, a cell or range reference, a label, a cell or range name, or
a function.
Formula Syntax and Operator Precedence. All elements in a formula must
follow a specific syntax or order. In Excel, the formula syntax is an equal
sign (=) followed by the operands (elements to be calculated) and operators.
For example, the formula =5+2 has a valid formula syntax.
Operator precedence refers to the rules that Excel uses to determine the
order of calculation. By default, Excel calculates a formula from left to
right. If a formula contains more than one operator, Excel will use the type
of operator to determine the order of calculation. Exponentiation
calculations are performed first, then multiplication and division, followed
by addition and subtraction, and finally the logical operators. If a formula
contains operators with the same precedence, Excel evaluates the operators
from left to right.
Here's an example of a formula using multiple operators =5+2*3. The result
of this calculation is 11 because Excel completes multiplication operations
before addition. It multiplies 2 by 3 (resulting in 6) and then adds 5.
Parentheses are used to override Excel's order of precedence. For example,
the formula =(5+2)*3 gives a result of 21. The parentheses direct Excel to
first add 5 and 2. It then multiplies that result by 3 for a result of 21.
For more information about the order in which Excel uses operators in
formulas, open Help in Excel. Choose the Answer Wizard tabbed page. Then,
type types of operators in the edit field, and press Enter.
What You Learned. In this topic, you learned:
In Excel, you use formulas to perform calculations on your data.
A formula is a mathematical expression that is comprised of numeric values,
cell references, functions, and operators. A formula's result changes when
other values referenced in the formula change.
All formulas begin with an equal sign. The equal sign directs Excel to treat
the data as a formula rather than as a constant value.
You should only use constant values in a formula when the value will not
change frequently.
A function is a pre-defined formula. Excel offers numerous functions to help
you analyze your data.
Operators are symbols that represent mathematical operations.
Operands are the elements to be calculated. An operand can be a constant
value, a cell or range reference, a label, a cell or range name, or a
function.
All elements in a formula must follow a specific syntax or order.
In Excel, the formula syntax is an equal sign (=) followed by the operands
(elements to be calculated) and operators.
By default, Excel calculates a formula from left to right. If a formula
contains more than one operator, Excel will use the operator precedence
rules to determine the order of calculation.
You can use parentheses to control the calculation order.
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