Crystal Reports for Eclipse Designer Guide

StdDev

Description
Enables you to find the standard deviation of a set of values in your report.
Overloads
  • StdDev (fld)
  • StdDev (fld, condFld)
  • StdDev (fld, condFld, cond)
  • StdDev (x)
  • Returns
    Number
    Action
    Enables you to find the standard deviation of a set of values in your report. For example:
  • You can calculate the grand total standard deviation for all values in a field.
  • You can calculate the standard deviation for all values within a group (for example, sales grouped by the state that they come from).
  • You can calculate the standard deviation for all values within a group in which grouping is controlled by changes in a date or Boolean field (for example, sales grouped by the month in which they were made).
  • If you specify a set of individual values, you can compute the standard deviation of the values in the set. For information on this kind of summary, see Array summary functions.
  • Examples
    StdDev({file.RESULTS})
    Calculates the standard deviation of all values in the Result field.
    StdDev({orders.AMOUNT}, {orders.CUSTOMER ID})
    Calculates the standard deviation for the orders in each group of orders in the Orders field. The orders are separated into groups whenever the value in the Customer field changes.
    StdDev({file.RESULTS}, {file.DATE}, "daily")
    Calculates the variation for each group of laboratory test results in the Results field. The test results are separated into groups whenever the value in the Date field changes to a new day.
    StdDev({file.SCORES}, {file.NATURALIZED}, "any change")
    Groups values in the Scores field based on whether or not the test taker is a naturalized citizen, and calculates the standard deviation for each group of scores.
    StdDev([({file.QTY1} * {file.PRICE1}),({file.QTY2} * {file.PRICE2}),({file.QTY3} * {file.PRICE3}), ({file.QTY4} * {file.PRICE4})])
    Returns 36.60 where Qty1 = 2, Price1 = 10.00, Qty2 = 2, Price2 = 2.00, Qty3 = 10, Price3 = 3.00, and Qty4 = 8, Price4 = 11.00.
    Comments
    Standard deviation is calculated using the following technique:
  • It calculates the average (mean) value for the items in the sample.
  • It subtracts the average value from the value of each item.
  • It squares the difference for each item.
  • It adds the squared differences for all of the items in the sample.
  • It divides the sum by one less than the number of items in the sample (N - 1). The result is the variance. Compare this step to the PopulationStdDev.
  • It calculates the square root of the variance to arrive at the standard deviation.
  • Using this function in a formula forces the formula to be evaluated at print time.
    For more information on evaluation time considerations, see Evaluation Time.



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