NAG C Library Function Document

nag_2d_panel_sort (e02zac)

1

Purpose

2

Specification

3

Description

A set of $m$ data points with rectangular Cartesian coordinates $x_r,y_r$ are sorted into panels defined by lines parallel to the $y$ and $x$ axes. The intercepts of these lines on the $x$ and $y$ axes are given in $\mathbf{lamda}\left[\mathit{i}-1\right]$, for $\mathit{i}=5,6,\dots ,\mathbf{px}-4$ and $\mathbf{mu}\left[\mathit{j}-1\right]$, for $\mathit{j}=5,6,\dots ,\mathbf{py}-4$, respectively. The function orders the data so that all points in a panel occur before data in succeeding panels, where the panels are numbered from bottom to top and then left to right, with the usual arrangement of axes, as shown in the diagram. Within a panel the points maintain their original order.

Figure 1

4

References

5

Arguments

1:    $\mathbf{px}$ – IntegerInput

2:    $\mathbf{py}$ – IntegerInput

On entry: px and py must specify eight more than the number of intercepts on the $x$ axis and $y$ axis, respectively.

Constraint: $\mathbf{px}\ge 8$ and $\mathbf{py}\ge 8$.

3:    $\mathbf{lamda}\left[\mathbf{px}\right]$ – const doubleInput

On entry: $\mathbf{lamda}\left[4\right]$ to $\mathbf{lamda}\left[\mathbf{px}-5\right]$ must contain, in nondecreasing order, the intercepts on the $x$ axis of the sides of the panels parallel to the $y$ axis.

4:    $\mathbf{mu}\left[\mathbf{py}\right]$ – const doubleInput

On entry: $\mathbf{mu}\left[4\right]$ to $\mathbf{mu}\left[\mathbf{py}-5\right]$ must contain, in nondecreasing order, the intercepts on the $y$ axis of the sides of the panels parallel to the $x$ axis.

5:    $\mathbf{m}$ – IntegerInput

On entry: the number $m$ of data points.

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

7:    $\mathbf{y}\left[\mathbf{m}\right]$ – const doubleInput

On entry: the coordinates of the $\mathit{r}$th data point $\left(x_{\mathit{r}},y_{\mathit{r}}\right)$, for $\mathit{r}=1,2,\dots ,m$.

8:    $\mathbf{point}\left[\mathit{dim}\right]$ – IntegerOutput

Note: the dimension, dim, of the array point must be at least $\left(\mathbf{m}+\left(\mathbf{px}-7\right)\times \left(\mathbf{py}-7\right)\right)$.

On exit: for $i=1,2,\dots ,\left(\mathbf{m}+\left(\mathbf{px}-7\right)\times \left(\mathbf{py}-7\right)\right)$, $\mathbf{point}\left[m+i-1\right]=\mathrm{I1}$ is the index of the first point in panel $i$, $\mathbf{point}\left[\mathrm{I1}-1\right]=\mathrm{I2}$ is the index of the second point in panel $i$ and so on.

$\mathbf{point}\left[\mathrm{In}-1\right]=0$ indicates that $\mathbf{x}\left[\mathrm{In}-1\right],\mathbf{y}\left[\mathrm{In}-1\right]$ was the last point in the panel.

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_ALLOC_FAIL

Dynamic memory allocation failed.
See Section 2.3.1.2 in How to Use the NAG Library and its Documentation for further information.

NE_BAD_PARAM

On entry, argument $〈\mathit{\text{value}}〉$ had an illegal value.

NE_INT

On entry, $\mathbf{m}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{m}>0$.

On entry, $\mathbf{px}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{px}\ge 8$.

On entry, $\mathbf{py}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{py}\ge 8$.

NE_INT_2

On entry, $\mathbf{px}=〈\mathit{\text{value}}〉$ and $\mathbf{py}=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{px}\ge 8$ and $\mathbf{py}\ge 8$.

NE_INTERNAL_ERROR

An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 2.7.6 in How to Use the NAG Library and its Documentation for further information.

NE_NO_LICENCE

Your licence key may have expired or may not have been installed correctly.
See Section 2.7.5 in How to Use the NAG Library and its Documentation for further information.

NE_NOT_NON_DECREASING

On entry, $\mathit{I}=〈\mathit{\text{value}}〉$, $\mathbf{lamda}\left[\mathit{I}-1\right]=〈\mathit{\text{value}}〉$ and $\mathbf{lamda}\left[\mathit{I}-2\right]=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{lamda}\left[\mathit{I}-1\right]\ge \mathbf{lamda}\left[\mathit{I}-2\right]$.

On entry, $\mathit{I}=〈\mathit{\text{value}}〉$, $\mathbf{mu}\left[\mathit{I}-1\right]=〈\mathit{\text{value}}〉$ and $\mathbf{mu}\left[\mathit{I}-2\right]=〈\mathit{\text{value}}〉$.
Constraint: $\mathbf{mu}\left[\mathit{I}-1\right]\ge \mathbf{mu}\left[\mathit{I}-2\right]$.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (e02zace.c)

10.2

Program Data

Program Data (e02zace.d)

10.3

Program Results

Program Results (e02zace.r)