GAMMAINV

Returns the inverse of the gamma cumulative distribution: if p = GAMMADIST(x,...), then GAMMAINV(p,...) = x.

Syntax

expression.GAMMAINV(arg1, arg2, arg3);

expression - A variable that represents a ApiWorksheetFunction class.

Parameters

Name	Required/Optional	Data type	Default	Description
arg1	Required	ApiRange | ApiName | number		The probability associated with the gamma distribution, a number between 0 and 1, inclusive.
arg2	Required	ApiRange | ApiName | number		The alpha parameter of the distribution, a positive number.
arg3	Required	ApiRange | ApiName | number		The beta parameter of the distribution, a positive number. If this parameter is equal to 1, the function returns the standard gamma distribution.

Returns

number

Example

Find the value that corresponds to a given probability in a gamma distribution in a spreadsheet.

// How do I calculate the inverse of a gamma cumulative distribution in a spreadsheet?

// Get the x-value for a probability point in a gamma distribution in a spreadsheet.

let worksheet = Api.GetActiveSheet();
let func = Api.WorksheetFunction;
let ans = func.GAMMAINV(0.4, 9, 2);
worksheet.GetRange("B2").SetValue(ans);