Crystal Reports for Eclipse Designer Guide

Variance

Description
Enables you to find the variance of a set of values in your report.
Overloads
  • Variance (fld)
  • Variance (fld, condFld)
  • Variance (fld, condFld, cond)
  • Variance (x)
  • Returns
    Number
    Action
    Enables you to find the variance of a set of values in your report. For example:
  • You can calculate the grand total variance for all values in a field.
  • You can calculate the variance for all values within a group (for example, sales grouped by the state that they come from).
  • You can calculate the variance 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 variance of the values in the set. For information on this kind of summary, see Array summary functions.
  • Examples
    Variance({file.AMOUNT})
    Calculates the variance of all values in the Amount field.
    Variance({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.
    Variance({file.SCORES}, {file.TEACHERS}) % Variance({file.SCORES})
    Groups values in the Scores field by teacher, and calculates the variance for each teacher group as a percentage of the variance of the values for the entire report (for all teachers listed).
    Variance([{file.QTY1}, {file.QTY2}, {file.QTY3}, {file.QTY4}])
    Returns 17.00 where Qty1 = 2, Qty2 = 2, Qty3 = 10, and Qty4 = 8.
    Comments
    Variance 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 final step to the PopulationVariance.
  • 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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