NAG C Library Function Document

nag_monotonic_deriv (e01bgc)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:    $\mathbf{n}$ – IntegerInput

On entry: n must be unchanged from the previous call of nag_monotonic_interpolant (e01bec).

2:    $\mathbf{x}\left[\mathbf{n}\right]$ – const doubleInput

3:    $\mathbf{f}\left[\mathbf{n}\right]$ – const doubleInput

4:    $\mathbf{d}\left[\mathbf{n}\right]$ – const doubleInput

On entry: x, f and d must be unchanged from the previous call of nag_monotonic_interpolant (e01bec).

5:    $\mathbf{m}$ – IntegerInput

On entry: $m$, the number of points at which the interpolant is to be evaluated.

Constraint: $\mathbf{m}\ge 1$.

6:    $\mathbf{px}\left[\mathbf{m}\right]$ – const doubleInput

On entry: the $m$ values of $x$ at which the interpolant is to be evaluated.

7:    $\mathbf{pf}\left[\mathbf{m}\right]$ – doubleOutput

On exit: $\mathbf{pf}\left[i\right]$ contains the value of the interpolant evaluated at the point $\mathbf{px}\left[\mathit{i}\right]$, for $\mathit{i}=0,1,\dots ,m-1$.

8:    $\mathbf{pd}\left[\mathbf{m}\right]$ – doubleOutput

On exit: $\mathbf{pd}\left[\mathit{i}\right]$ contains the first derivative of the interpolant evaluated at the point $\mathbf{px}\left[\mathit{i}\right]$, for $\mathit{i}=0,1,\dots ,m-1$.

9:    $\mathbf{fail}$ – NagError *Input/Output

The NAG error argument (see Section 3.7 in How to Use the NAG Library and its Documentation).

6

Error Indicators and Warnings

NE_INT_ARG_LT

On entry, $\mathbf{m}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m}\ge 1$.

On entry, $\mathbf{n}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{n}\ge 2$.

NE_NOT_MONOTONIC

On entry, $\mathbf{x}\left[r-1\right]\ge \mathbf{x}\left[r\right]$ for $r=〈\mathit{\text{value}}〉$ : $\mathbf{x}\left[r-1\right]=〈\mathit{\text{value}}〉$, $\mathbf{x}\left[r\right]=〈\mathit{\text{value}}〉$.
The values of $\mathbf{x}\left[\mathit{r}\right]$, for $\mathit{r}=0,1,\dots ,n-1$, are not in strictly increasing order.

NW_EXTRAPOLATE

Warning – some points in array px lie outside the range $\mathbf{x}\left[0\right]\dots \mathbf{x}\left[n-1\right]$. Values at these points are unreliable as they have been computed by extrapolation.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (e01bgce.c)

10.2

Program Data

Program Data (e01bgce.d)

10.3

Program Results

Program Results (e01bgce.r)