Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Deriving Information from the Table

Having attribute information in table form allows you to obtain statistics, to search for specific text strings, and to sort the information.

____ 11. You can find out the average of the values of a column along with the count of the number of values, minimum, maximum, sum, and standard deviation.19 To do so, you right-click the column heading to bring up a menu of choices from which you choose Statistics. For example, select the column FLOW_RATE by placing the mouse pointer over the heading of the column (the pointer becomes a down-pointing arrow) and right-clicking. (You may have to use the scroll bar at the bottom of the table to find the FLOW_RATE column.) Choose Statistics from the drop-down menu. You see information about the values in the column from the Statistics of Fire_Hydrants window. There are 21 values. The minimum flow rate is 250. What is the maximum flow rate? ________. You also receive a frequency diagram that shows the number of hydrants that have each given value (e.g. there are four hydrants with a low flow rate, nine with a moderately high rate, and eight with a high rate). If all the hydrants were turned on at once, how much water would flow? __________. The mean (i.e., average) and standard deviation, although they probably don’t mean much in this situation, are about 356 and 54, respectively.

____ 12. Once you have the Statistics window up, you can determine the statistics of other columns by selecting the column ...