A histogram is a bar graph that displays how often numbers within a given range appear in a data set. The frequency formula, coupled with the index formula in Apple's iWork Numbers, allows you to quickly calculate the frequency for a range of numbers contained within a data set. To use the frequency and index formulas, you must set up the spreadsheet by adding a section that contains the data, creating a list that contains the highest number in each range, and assigning a number to each interval-value.

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## Create Frequency Function

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Enter the data that contains the information for the histogram. Create a list of the interval-values by entering the highest number of the interval into each cell.

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Assign a number beginning with "1" to the interval-values by typing the number next to or below the interval-values. Continue assigning numbers to one cell past the highest interval-value.

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Enter the frequency formula for the first interval-value. Position the cursor in an empty cell next to or below the interval-value interval-value number. Type "=INDEX(FREQUENCY($data cells, $interval-value cells), interval-value number)." Replace "data cells" with the absolute cell locations that contains the data. Replace "interval-value" cells with the absolute cell locations that contain the interval-values. Replace "interval-value number" with the relative cell location for the first interval-value number. The formula will count all of the numbers that fall within the interval-value.

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Copy the cell that contains the formula. Paste the formula into all of the cells next to or below the interval-value numbers. You will now have a list of frequencies for each interval-value.

## Create Histogram

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Select the range of cells that contain the frequencies.

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Click the "Insert" menu, move your cursor over "Chart" and select "Column." A chart will appear with the frequency numbers displayed in columns.

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Double-click on the first x-axis title. Type the name for the title, such as the first interval-value. Enter the remaining x-axis titles in the same way.