GAMMALN()

Syntax. GAMMALN(x)

Definition. This function returns the natural logarithm of the gamma function (Γ(x)).

Arguments

  • x (required). The value for which you want to calculate GAMMALN()

Note

If x isn’t a numeric expression, the GAMMALN() function returns the #VALUE! error. If x is less than or equal to 0, the function returns the #NUM! error.

The number e raised to the GAMMALN(i) power, where i is an integer, returns the same result as (i – 1).

Background. The GAMMALN() function returns the natural logarithm of the gamma function.

See Also

You will find more information about gamma distributions in the description of GAMMA.DIST().

The logarithm of a number is the exponent by which a fixed number, the base, has to be raised to produce that number. The following logarithms exist:

  • Natural logarithm to base e (Euler’s number = 2.72)

  • Logarithm to base 10

  • Logarithm to base 2

The logarithm (to base b) of a number y is the number by which base b has to be raised to produce number y. Therefore, the logarithm is an exponent, and the logarithm function is the inverse function of the exponential function (see Figure 12-66).

The logarithm function.

Figure 12-66. The logarithm function.

GAMMALN() is calculated as follows:

image with no caption

where

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ExampleAssume that you want to calculate GAMMALN() given the value 4. Figure 12-67 shows the calculation of GAMMALN().

Calculating GAMMALN().

Figure 12-67. Calculating GAMMALN().

The GAMMALN() function returns the natural logarithm, 1.7918, for the gamma function based on the parameters shown in Figure 12-67.

See Also

FACT(), GAMMA.DIST()

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