recalculate values after editing a cell

To use formulas efficiently, there are three important considerations you need to understand:

Calculation is the process of computing formulas and then displaying the results as values in the cells that contain the formulas. To avoid unnecessary calculations, Microsoft Office Excel automatically recalculates formulas only when the cells that the formula depends on have changed. This is the default behavior when you first open a workbook and when you are editing a workbook. However, you can control when and how Excel recalculates formulas.

Iteration is the repeated recalculation of a worksheet until a specific numeric condition is met. Excel cannot automatically calculate a formula that refers to the cell — either directly or indirectly — that contains the formula. This is called a circular reference. If a formula refers back to one of its own cells, you must determine how many times the formula should recalculate. Circular references can iterate indefinitely. However, you can control the the maximum number of iterations and the amount of acceptable change.

Precision is a measure of the degree of accuracy for a calculation. Excel stores and calculates with 15 significant digits of precision. However, you can change the precision of calculations so that Excel uses the displayed value instead of the stored value when it recalculates formulas.

Replace a formula with its result

You can convert the contents of a cell that contains a formula so that the calculated value replaces the formula. If you want to freeze only part of a formula, you can replace only the part you don't want to recalculate. Replacing a formula with its result can be helpful if there are many or complex formulas in the workbook and you want to improve performance by creating static data.

You can convert formulas to their values on either a cell-by-cell basis or convert an entire range at once.

Important Make sure you examine the impact of replacing a formula with its results, especially if the formulas reference other cells that contain formulas. It's a good idea to make a copy of the workbook before replacing a formula with its results.

Replace formulas with their calculated values

Caution When you replace formulas with their values, Microsoft Office Excel permanently removes the formulas. If you accidentally replace a formula with a value and want to restore the formula, click Undo immediately after you enter or paste the value.

1. Select the cell or range of cells that contains the formulas.

   If the formula is an array formula (array formula: A formula that performs multiple calculations on one or more sets of values, and then returns either a single result or multiple results. Array formulas are enclosed between braces { } and are entered by pressing CTRL+SHIFT+ENTER.), select the range that contains the array formula.

   How to select a range that contains the array formula

   1. Click a cell in the array formula.
   2. On the Home tab, in the Editing group, click Find & Select, and then click Go To.
   3. Click Special.
   4. Click Current array.
2. Click Copy .
3. Click Paste .
4. Click the arrow next to Paste Options , and then click Values Only.

The following example shows a formula in cell D2 that multiplies cells A2, B2, and a discount derived from C2 to calculate an invoice amount for a sale. To copy the actual value instead of the formula from the cell to another worksheet or workbook, you can convert the formula in its cell to its value by doing the following:

1. Press F2 to edit the cell.
2. Press F9, and then press ENTER.

   

   After you convert the cell from a formula to a value, the value appears as 1932.322 in the formula bar. Note that 1932.322 is the actual calculated value, and 1932.32 is the value displayed in the cell in a currency format.

   

   Tip When you are editing a cell that contains a formula, you can press F9 to permanently replace the formula with its calculated value.

Replace part of a formula with its calculated value

There may be times when you want to replace only a part of a formula with its calculated value. For example, you want to lock in the value that is used as a down payment for a car loan. That down payment was calculated based on a percentage of the borrower's annual income. For the time being, that income amount won't change, so you want to lock the down payment in a formula that calculates a payment based on various loan amounts.

Caution When you replace a part of a formula with its value, that part of the formula cannot be restored.

1. Click the cell that contains the formula.
2. In the formula bar (formula bar: A bar at the top of the Excel window that you use to enter or edit values or formulas in cells or charts. Displays the constant value or formula stored in the active cell.) , select the portion of the formula that you want to replace with its calculated value. When you select the part of the formula that you want to replace, make sure that you include the entire operand (operand: Items on either side of an operator in a formula. In Excel, operands can be values, cell references, names, labels, and functions.). For example, if you select a function, you must select the entire function name, the opening parenthesis, the arguments (argument: The values that a function uses to perform operations or calculations. The type of argument a function uses is specific to the function. Common arguments that are used within functions include numbers, text, cell references, and names.), and the closing parenthesis.
3. To calculate the selected portion, press F9.
4. To replace the selected portion of the formula with its calculated value, press ENTER.

   If the formula is an array formula (array formula: A formula that performs multiple calculations on one or more sets of values, and then returns either a single result or multiple results. Array formulas are enclosed between braces { } and are entered by pressing CTRL+SHIFT+ENTER.), press CTRL+SHIFT+ENTER.

http://office.microsoft.com/en-gb/excel/HP100541491033.aspx

http://office.microsoft.com/en-gb/excel/HP100662581033.aspx?pid=CH100648421033#Replace%20a%20formula%20with%20its%20calculated%20value

Comparison Operators

You can compare two values with the following operators. When two values are compared by using these operators, the result is a logical value either TRUE or FALSE.

http://office.microsoft.com/en-gb/excel/HP100788861033.aspx?pid=CH100648411033

use built-in functions with a minimum set providing the equivalent of

Arithmetic:	SUM, MAXIMUM, MINIMUM, COUNT, ABSOLUTE VALUE, SQUARE ROOT, INTEGER PART
Statistical:	MEAN, STANDARD DEVIATION
Logical:	IF (allows selection of a value on the basis of a simple relation being TRUE or FALSE)
Other:	LOOKUP

enter formulas into cells to calculate values

To perform basic mathematical operations such as addition, subtraction, or multiplication; combine numbers; and produce numeric results, use the following arithmetic operators.
Examples of these arithmetic operators were seen in the previous post "use arithmetic operators to create formulas"













The link listed below is a useful tutorial on how to use excel as a simple arithmetic calculator by producing formulas and entering them into cells to calculate values
http://phoenix.phys.clemson.edu/tutorials/excel/arithmetic.html

use arithmic operators to create formulas

To perform basic mathematical operations such as addition, subtraction, or multiplication; combine numbers; and produce numeric results, use the following arithmetic operators which are shown in the table below

1. Decide what your formula needs to calculate. Do you need to add up a column or row of figures? Do you need to divide one cell's value by another cell's value?
2. Start with an “=” (equal sign). Every formula will start with an equal sign. If you don't begin with this symbol, your formula will not work.
3. Put the first cell's name next. Each cell has a name assigned to it. “A1” is the first cell in the worksheet. Find the cell name by looking at the row and column that it is in.
4. Use the correct function key: “*” for multiplication, “/” for division, “+” is for addition and “-“ for subtraction.
5. Insert the last cell name. This is just like a math problem. Use the same rules as a simple math problem and your formula will work for you.
6. Hit “Enter.” Does your formula work? Double-check to make sure the components of the formula are correct.

http://office.microsoft.com/en-us/excel/HP051986971033.aspx

copy (replicate) cells using both absolute and relative referencing

Relative Cell References

This is the most widely used type of cell reference in formulas. Relative cell references are basic cell references that adjust and change when copied or when using AutoFill. In more simple terms, the cells are adjusted using the same formula from the previous cell references to the other cells intended to be adjusted and changed according with the formula.

Example:
=SUM(B5:B8), as shown below, changes to =SUM(C5:C8) when copied across to the next cell.

Absolute Cell References
Situations arise in which the cell reference must remain the same when copied or when using AutoFill. Dollar signs are used to hold a column and/or row reference constant.

Example:
In the example below, when calculating commissions for sales staff, you would not want cell B10 to change when copying the formula down. You want both the column and the row to remain the same to refer to that exact cell. By using $B$10 in the formula, neither changes when copied.

http://web.pdx.edu/~stipakb/CellRefs.htm

enter text, numeric values and formulas into cells

• Text that is typed will always appear in the active cell the same will happen for numeric values and formulas (which will calculate by hitting enter). More simply when you click a cell, the text, numeric values and formulas you type will appear in this cell.
  
• Click the cell where you want the text to appear. The bold border moves to this cell, showing that it is the active cell.

• Type the text. What you type appears in the active cell and in the formula bar. If you make a mistake while typing, press Backspace and correct it.
  When you have completed the contents for one cell, press Enter.