Routines (alphabetical) > Routines: C > CRVLENGTH

# CRVLENGTH

The CRVLENGTH function computes the length of a curve with a tabular representation, Y[i] = F(X[i]).

Note: Data that is highly oscillatory requires a sufficient number of samples for an accurate curve length computation.

This routine is written in the IDL language. Its source code can be found in the file `crvlength.pro` in the `lib` subdirectory of the IDL distribution.

## Example

;Define a 21-element vector of X-values:
x = [-2.00, -1.50, -1.00, -0.50, 0.00, 0.50, 1.00, 1.50, 2.00, $
2.50, 3.00, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, $
7.00, 7.50, 8.00]
;Define a 21-element vector of Y-values:
y = [-2.99, -2.37, -1.64, -0.84, 0.00, 0.84, 1.64, 2.37, 2.99, $
3.48, 3.86, 4.14, 4.33, 4.49, 4.65, 4.85, 5.13, 5.51, $
6.02, 6.64, 7.37]
;Compute the length of the curve:
result = CRVLENGTH(x, y)
Print, result

IDL prints:

14.8115

## Syntax

Result = CRVLENGTH( X, Y [, /DOUBLE] )

## Return Value

Returns the curve length.

## Arguments

### X

An n-element vector containing the independent variable values. X may be of type integer, floating point, or double-precision floating-point. X must contain at least three elements, and values must be specified in ascending order. Duplicate X values will result in a warning message.

### Y

An n-element single- or double-precision floating-point vector.

## Keywords

### DOUBLE

Set this keyword to force the computation to be done in double-precision arithmetic.

## Version History

5.0 | Introduced

## See Also

INT_TABULATED, PNT_LINE