NAG Library Routine Document

G01AJF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     X(N) – REAL (KIND=nag_wp) arrayInput

On entry: the data values.

2:     N – INTEGERInput

On entry: the number of data values.

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

3:     NSTEPX – INTEGERInput/Output

On entry: the number of character positions to be used in the horizontal direction, i.e., the number of categories in the histogram.

On exit: if $\mathbf{NSTEPX}<10$ on entry, NSTEPX is reset to $10$.

If $\mathbf{NSTEPX}>99$ on entry, NSTEPX is reset to $99$.

Otherwise, NSTEPX is unchanged on exit.

4:     NSTEPY – INTEGERInput/Output

On entry: the number of character positions to be used in the vertical direction, i.e., the maximum height of a histogram bar.

On exit: if $\mathbf{NSTEPY}<10$ on entry, NSTEPY is reset to $10$.

If $\mathbf{NSTEPY}>99$ on entry, NSTEPY is reset to $99$.

Otherwise, NSTEPY is unchanged on exit.

5:     ITYPE – INTEGERInput

On entry: indicates whether a histogram of frequencies or cumulative frequencies is required.

$\mathbf{ITYPE}=0$ for frequencies.

$\mathbf{ITYPE}\ne 0$ for cumulative frequencies.

The second option effectively displays the distribution function of the data rather than the density function.

6:     ISPACE – INTEGERInput/Output

On entry: indicates how many spaces are to be inserted at the beginning of each output line.

If $\mathbf{ISPACE}<0$ on input, $\mathbf{ISPACE}=0$ is used

If $\mathbf{ISPACE}+\mathbf{NSTEPX}+14>120$, then $\mathbf{ISPACE}=0$ is used.

The second condition imposes an effective line length limit of $120$ characters.

On exit: unchanged unless $\mathbf{ISPACE}<0$ or $\mathbf{ISPACE}+\mathbf{NSTEPX}+14>120$, in which case ISPACE is set to $0$.

7:     XMIN – REAL (KIND=nag_wp)Input/Output

8:     XMAX – REAL (KIND=nag_wp)Input/Output

On entry: if $\mathbf{XMIN}<\mathbf{XMAX}$, only those values in X such that $\mathbf{XMIN}\le \mathbf{X}\left(\mathit{i}\right)\le \mathbf{XMAX}$, for $\mathit{i}=1,2,\dots ,n$, are included in the histogram.

If $\mathbf{XMIN}\ge \mathbf{XMAX}$, all the data are included.

On exit: if $\mathbf{XMIN}<\mathbf{XMAX}$ on entry, then XMIN and XMAX are unchanged.

If $\mathbf{XMIN}\ge \mathbf{XMAX}$ then XMIN and XMAX contain the minimum and maximum data values respectively.

9:     XSTEP – REAL (KIND=nag_wp)Output

On exit: the width of each class interval.

10:   N1 – INTEGEROutput

On exit: the total number of observations actually included in the histogram.

11:   MULTY – INTEGEROutput

On exit: the number of observations represented by each * in the histogram.

12:   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,

$\mathbf{N}<1$.

7  Accuracy

8  Further Comments

9  Example

9.1  Program Text

Program Text (g01ajfe.f90)

9.2  Program Data

Program Data (g01ajfe.d)

9.3  Program Results

Program Results (g01ajfe.r)