WorksheetFunction.GammaDist Method
Returns the gamma distribution. You can use this function to study variables that may have a skewed distribution. The gamma distribution is commonly used in queuing analysis.
Namespace: Microsoft.Office.Interop.Excel
Assembly: Microsoft.Office.Interop.Excel (in Microsoft.Office.Interop.Excel.dll)
Syntax
'Declaration
Function GammaDist ( _
Arg1 As Double, _
Arg2 As Double, _
Arg3 As Double, _
Arg4 As Boolean _
) As Double
'Usage
Dim instance As WorksheetFunction
Dim Arg1 As Double
Dim Arg2 As Double
Dim Arg3 As Double
Dim Arg4 As Boolean
Dim returnValue As Double
returnValue = instance.GammaDist(Arg1, _
Arg2, Arg3, Arg4)
double GammaDist(
double Arg1,
double Arg2,
double Arg3,
bool Arg4
)
Parameters
Arg1
Type: System.DoubleX - the value at which you want to evaluate the distribution.
Arg2
Type: System.DoubleAlpha - a parameter to the distribution.
Arg3
Type: System.DoubleBeta - a parameter to the distribution. If beta = 1, GammaDist returns the standard gamma distribution.
Arg4
Type: System.BooleanCumulative - a logical value that determines the form of the function. If cumulative is true, GammaDist returns the cumulative distribution function; if false, it returns the probability density function.
Return Value
Type: System.Double
Remarks
Important
This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. This function is still available for compatibility with earlier versions of Excel. However, if backward compatibility is not required, you should consider using the new functions from now on, because they more accurately describe their functionality.For more information about the new function, see the Gamma_Dist(Double, Double, Double, Boolean) method.
If x, alpha, or beta is nonnumeric, GammaDist returns the #VALUE! error value.
If x < 0, GammaDist returns the #NUM! error value.
If alpha ≤ 0 or if beta ≤ 0, GammaDist returns the #NUM! error value.
The equation for the gamma probability density function is:
Figure 1: Gamma probability density function
.jpg "Gamma probability density function")
The standard gamma probability density function is:
Figure 2: Standard gamma probability density function
.jpg "Standard gamma probability density function")
When alpha = 1, GammaDist returns the exponential distribution with:
Figure 3: Equation
.jpg "Equation")
For a positive integer n, when alpha = n/2, beta = 2, and cumulative = true, GammaDist returns (1 - CHIDIST(x)) with n degrees of freedom.
When alpha is a positive integer, GammaDist is also known as the Erlang distribution.