NAG Library Routine Document

G01AGF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     $\mathrm{X}\left(\mathbf{NOBS}\right)$ – REAL (KIND=nag_wp) arrayInput

On entry: the values to be plotted in the $x$-direction.

2:     $\mathrm{Y}\left(\mathbf{NOBS}\right)$ – REAL (KIND=nag_wp) arrayInput/Output

On entry: the values to be plotted in the $y$-direction.

On exit: the elements of Y are sorted into descending order of magnitude.

3:     $\mathrm{NOBS}$ – INTEGERInput

On entry: the number of observations to be plotted.

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

4:     $\mathrm{ISORT}\left(\mathbf{NOBS}\right)$ – INTEGER arrayOutput

On exit: the key to the descending order of the elements in array Y, i.e., $\mathbf{ISORT}\left(\mathit{i}\right)$ contains the position of the value $\mathbf{Y}\left(\mathit{i}\right)$ in the original array Y, for $\mathit{i}=1,2,\dots ,\mathbf{NOBS}$.

5:     $\mathrm{NSTEPX}$ – INTEGERInput

On entry: the number of steps (character positions) to be plotted in the $x$-direction. If the supplied value of NSTEPX is less than $10$, the value $10$ will be used by G01AGF. The maximum value for NSTEPX is the number of character positions available on the chosen output device less $15$, up to a maximum of $133$. If NSTEPX exceeds $133$ on input, the value $133$ will be used by the routine.

6:     $\mathrm{NSTEPY}$ – INTEGERInput

On entry: the number of steps (character positions) to be plotted in the $y$-direction. If the supplied value of NSTEPY is less than $10$, the value $10$ will be used by G01AGF. There is no maximum value for NSTEPY, but you should bear in mind that $\left(\mathbf{NSTEPY}+5\right)$ records (lines) of output are generated by the routine.

7:     $\mathrm{IFAIL}$ – INTEGERInput/Output

On entry: IFAIL must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ is used it is essential to test the value of IFAIL on exit.

On exit: $\mathbf{IFAIL}=\mathbf{0}$ unless the routine detects an error or a warning has been flagged (see Section 6).

6  Error Indicators and Warnings

$\mathbf{IFAIL}=1$

On entry,

$\mathbf{NOBS}<1$.

$\mathbf{IFAIL}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

See Section 3.8 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-399$

Your licence key may have expired or may not have been installed correctly.

See Section 3.7 in the Essential Introduction for further information.

$\mathbf{IFAIL}=-999$

Dynamic memory allocation failed.

See Section 3.6 in the Essential Introduction for further information.

7  Accuracy

8  Parallelism and Performance

9  Further Comments

10  Example

10.1  Program Text

Program Text (g01agfe.f90)

10.2  Program Data

Program Data (g01agfe.d)

10.3  Program Results

Program Results (g01agfe.r)