Name
Log Function
Class
System.Math
Syntax
Math.Log(d
)
or:
Math.Log(a, newbase
)
-
d
ora
Use: Required
Data Type: Double
A numeric expression greater than zero
-
newbase
Use: Required
Data Type: Double
The base of the logarithm
Return Value
Double
Description
Returns the natural (base e) logarithm of a given number (the first syntax) or the logarithm of a given number in a specified base (the second syntax)
Rules at a Glance
The natural logarithm is the logarithm base e, a constant whose value is approximately 2.718282. The natural logarithm satisfies the equation:
e^Log(x) = x
In other words, the natural logarithm function is the inverse function of the exponential function.
d
ora
, the value whose natural logarithm the function is to return, must be a positive real number. If number is negative or zero, the function generates runtime error 5, “Invalid procedure call or argument.”This is a Shared member, so it can be used without creating any objects.
Programming Tips and Gotchas
You can calculate base-
n
logarithms for any number,x
, by dividing the natural logarithm ofx
by the natural logarithm ofn
, as the following expression illustrates:Logn(x) = Log(x) / Log(n)
For example, the Log10 function shows the source code for a custom function that calculates base-10 logarithms:
Static Function Log10(X) Log10 = Log(X) / Log(10#) End Function
The inverse trigonometric functions, which are not intrinsic to VB, can be computed using the value returned by the
Log
function. The functions and their formulas ...
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