WINDROSE procedure

Plots rose diagrams of circular data like wind speeds (P.W. Goedhart & R.W. Payne).

Options

PRINT = string

What to print (table); default * i.e. nothing

SEGMENT = scalar

Width of sectors (in degrees) into which to group an ANGLES variates before plotting; default 45

MSEGMENT = scalar

Defines the centre (in degrees) of the sectors; default 0

INTERVALS = scalar or variate

Scalar to define the intervals at which to summarize the data values, or a variate defining the boundaries between the intervals; default * i.e. determined automatically

%INTERVAL = scalar

Interval (on the percent scale) between the circles drawn to provide a scale on the diagram

COLOURS = variate

Colours to shade the triangles segment for each interval; default !(2, 3...)

SCREEN = string

Whether to clear screen before displaying the graphs (keep, clear); default clea

Parameters

DATA = variates

Data values

ANGLES = factors or variates

Directions of the data values

TITLE = text

Title for the graph; default * i.e. identifier of the DATA variate

WINDOW = scalar

Window for the graph; default 3

Description

WINDROSE plots data, like wind speeds, that are observed at angles around a circle. The data values are supplied in a variate by the DATA parameter. The angles at which the data values were observed are specified by ANGLES parameter. If this is set to a variate, WINDROSE groups the observations into sectors of width specified (in degrees) by the SEGMENT option, with centres defined by the MSEGMENT option. The sectors are centred at MSEGMENT, MSEGMENT+SEGMENT, MSEGMENT+2*SEGMENT, and so on. The default values for SEGMENT and MSEGMENT are 45 and 0 respectively. Alternatively, ANGLES can be set to a factor; its levels then define the midpoints of the sectors (and these must be in clockwise order).

WINDROSE categorizes the data values by determining the number of observations within a set of intervals specified by the INTERVALS option. The option can supply a variate specifying the lower boundaries of the intervals, or a scalar defining boundaries at multiples of the value that it contains. The diagram has a circular segment for each direction, with radius equal to the percentage of the total observations that are in that direction. To indicate the distribution of the data values in that direction, the segment is subdivided into a section for each interval. The sections are shaded in colours, which can be specified by the COLOURS option; by default, the colours 2, 3... are used. Zero, negative or missing values of the DATA variate are assumed to represent "calm" values. These are represented by an empty circle at the centre of the diagram. Circles are drawn at intervals around this inner circle to provide a scale. The intervals between these circles are specified by the %INTERVAL option. You can also print the information, as a two-way table (directions × intervals) by setting option PRINT=table.

The parameters allow several rose diagrams to be plotted at once. The SCREEN option controls whether the existing screen is kept or cleared before plotting begins; by default SCREEN=clear. The WINDOW parameter specifies the graphics window in which each diagram is plotted. If these are not specified, the FFRAME procedure is used to set up a rectangular array with a window for each diagram. The TITLE parameter can be used to supply a title for each plot; if this is not specified, the identifier of the DATA variate is used.

Options: PRINT, SEGMENT, MSEGMENT, INTERVALS, %INTERVAL, COLOURS, SCREEN.

Parameters: DATA, ANGLES, TITLE, WINDOW.

Method

WINDROSE uses GenStat's standard graphics and calculation commands.

Action with RESTRICT

If DATA or ANGLES are restricted, only the unrestricted units are used.