The frequency function calculates how often values occur within a range of values, and then returns a vertical array of numbers. For example, use FREQUENCY to count the number of test scores that fall within ranges of scores. Because FREQUENCY returns an array, it must be entered as an array formula.
1. Click on an open cell in your spreadsheet where you would like the frequency table to appear.
2. Open the function wizard and select the frequency function. You will see a dialog box that looks like the following:
3. Click on the 
for Data_array
and highlight the data to be summarized.
4. Click on the for Bins_array
and highlight the categories to be summarized.
5. Click on 
.
6. You now have a cell with the frequency formula in it. Copy the formula from the cell using the 
icon.
7. Highlight a group of cells that is one larger than the size of your Bins_array. Paste the formula into these cells by pressing shift+insert. Then press the shift+ctrl+enter keys at the same time. This will create the frequency array.
An array formula can perform multiple calculations and then return either a single result or multiple results.
Array formulas act on two or more sets of values known as array arguments. Each array argument must have the same
number of rows and columns. You create array formulas the same way that you create basic, single-value formulas.
Select the cell or cells that will contain the formula, create the formula, and then press CTRL+SHIFT+ENTER to
enter the formula.
If you want only a single result, Microsoft Excel may need to perform several calculations to generate that result.
For example, the following formula averages only the cells in the range D5:D15 where the cell in the same row in
column A contains the text "Blue Sky Airlines". The IF function finds the cells in the range A5:A15 that
contain "Blue Sky Airlines" and then returns the value in the corresponding cell in D5:D15 to the AVERAGE
function.
{=AVERAGE(IF(A5:A15="Blue Sky Airlines",D5:D15))}
To calculate multiple results with an array formula, you must enter the array into a range of cells that has the
same number or rows and columns as the array arguments. In the following example, given a series of five sales
figures (in column B) for a series of five dates (in column A), the TREND function determines the straight-line
values for the sales figures. To display all of the results of the formula, it is entered into five cells in column
C (C10:C15).
{=TREND(B10:B15,A10:A15)}
You can also use an array formula to calculate single or multiple results for a series of values that have not
been entered on the worksheet. Array formulas can accept constants the same way nonarray formulas do, but you must
enter the array constants in a certain format. For example, given the same five values and the same five dates
in the preceding example, you can project the sales figures for two additional dates in the future. Because formulas
or functions cannot be array constants, the following example uses serial numbers to represent the additional dates
for the third argument in the TREND function:
{=TREND(B10:B15,A10:A15,{35246;35261})}