IMSL_ELRC

Syntax | Return Value | Arguments | Keywords | Discussion | Example | Version History

The IMSL_ELRC function evaluates an elementary integral from which inverse circular functions, logarithms and inverse hyperbolic functions can be computed.

Note
This routine requires an IDL Advanced Math and Stats license. For more information, contact your ITT Visual Information Solutions sales or technical support representative.

Syntax

Result = IMSL_ELRC(x, y [, /DOUBLE])

Return Value

The elliptic integral R_C (x, y).

Arguments

x

First argument for which the function value is desired. It must be nonnegative and must satisfy the conditions given below.

y

Second argument for which the function value is desired. It must be nonnegative and must satisfy the conditions given below.

Keywords

DOUBLE

If present and nonzero, double precision is used.

Discussion

Carlson's elliptic integral of the third kind is defined to be:

The argument x must be nonnegative, y must be positive, and x + y must be less than or equal to b/5 and greater than or equal to 5s. If any of these conditions are false, the IMSL_ELRC is set to b. Here, b is the largest and s is the smallest representable floating-point number.

The IMSL_ELRC function is based on the code by Carlson and Notis (1981) and the work of Carlson (1979).

Example

The integral R_C (2.25, 2) is computed.

PRINT, IMSL_ELRC(2.25, 2.0) 
     0.693147 

Version History