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Manual page for proc_scatterplot(PL)
DESCRIPTION
Displays data points in one or two dimensions.
FEATURES
Clustering (using a small offset) of duplicate data points.
Data points may be marked with geometric point symbols,
characters/text, or lines.
User control over point shapes, colors, sizes.
Optional labelling from data, and control of point size from data.
HTML clickmap
support for data points.
EXAMPLES
See the Gallery Scatterplot page
VARIABLES THAT ARE SET
NVALUES = the number of in-range plottable points that were rendered.
Note: this may be used in the legendlabel.
UNPLOTTABLE DATA
proc scatterplot will omit data points that are not valid
or not within the plotting area.
PREREQUISITES
A plotting area must be set up using proc areadef
and proc getdata must be executed to
access or define some data.
MODES
2-dimensional (2-D) and 1-dimensional (1-D).
For 2-D scatterplots, both xfield and yfield
should be specified.
With 1-D scatterplots points are plotted along an imaginary
line. To distribute points horizontally along Y=1 for example,
ylocation: 1 and xfield should be specified.
To distribute points vertically along X=5,
xlocation: 5 and yfield should be specified.
Data points may be marked with geometric point symbols and/or
characters/text, or using short line segments.
Characters/text may be a literal or it may come from a data field.
It is also possible to have the geometric point symbols under the
control of a datafield (symfield).
DUPLICATE POINTS
The cluster attribute (which is on by default) causes
duplicate points to be offset slightly to form a cluster or bar, which
often gives a satisfactory visual representation of the degree
of duplicity.
It is also possible to show duplicity using different symbol colors,
sizes or shapes (dupsleg).
MANDATORY ATTRIBUTES
For a 2-D scatterplot both xfield and yfield must
be specified.
For a 1-D scatterplot, either xfield or yfield must
be specified.
ATTRIBUTES
xfield
dfield
Get X plotting values from this data field.
First field is 1.
Example: xfield: 1
yfield
dfield
Get Y plotting values from this data field.
First field is 1.
Example: yfield: 1
xlocation
locvalue
If specified, proc scatterplot will operate in 1-D mode
along Y. The value specifies where the points will be rendered in X.
ylocation
locvalue
If specified, proc scatterplot will operate in 1-D mode
along X. The value specifies where the points will be rendered in Y.
cluster yes | no
If yes, data will be sorted on X,Y and duplicate data points
will be detected and offset slightly to show duplicity.
The default is yes.
Clusters may be as large as N=36 (after this, points will overlap).
Additional attributes related to clustering are described below.
Note: If labelfield and/or sizefield are being used, clustering
will work properly only when data are presorted into X,Y order.
symbol
symboldetails
If specified, a geometric point symbol will mark data points.
This specifies the attributes of the symbols to be used.
Example: symbol: style=fill shape=circle fillcolor=red
linelen n
If specified, data points will be displayed as lines of length
n in
absolute units
. The direction of the line will
be appropriate for 1-D scatterplots; for 2-D it is horizontal.
Line color, etc. may be controlled using linedetails.
Example: linelen: 0.2
text
text
If specified, data points will be displayed using the
given text, centered around the data point.
This attribute may be used with or without a symbol.
Example: text: A
labelfield
dfield
If specified, data points will be displayed using
the contents of data field dfield, centered
around the data point.
May not be used with symbol; in order to do datafield-driven label
plus a symbol proc scatterplot must be invoked twice.
Example: labelfield: 4
textdetails
textdetails
Details concerning the rendering of point labels.
Example: textdetails: size=6
linedetails
linedetails
If points are displayed using line segments (linelen), this
attribute allows control of color, line width, etc.
legendlabel
text
A label to be associated with the current set of points in the legend.
proc legend must be executed later in order to
render the legend. @NVALUES may be used to signify number of
points rendered.
Example: legendlabel: Group 4, N=@NVALUES
verticaltext yes | no
If yes, label text will be rendered vertically.
This might be useful when labels are > 1 character long
and data are close together in X.
sizefield
dfield
Allows the size of point markers or lines to be controlled by
a datafield, effectively allowing another variable to be presented.
If data points are marked using geometric symbols or text,
the value in dfield will cause the marks to correspond
to character point sizes. For example, a data value
of 10 would yield a data point mark 10 points in height.
The sizescale attribute may be used to scale the
sizefield data appropriately.
If data points are marked using lines, the value in dfield
will scale the length of the lines. For example, a data value
of 1.0 would leave the line length unchanged, while 2.0 would
double it and 0.5 would halve it.
sizescale n
May be used with sizefield when the size of data point symbols or text is
being controlled by a datafield. This attribute may be used
to scale the size of the point symbols to the desired range.
It assumes the symbol is a circle and scales the area rather than
the diameter or radius.
A value of 1.0 would leave the size unchanged,
while 2.0 would double the resulting size,
and 0.5 would halve it.
clustermethod 2d | horiz | vert | upward | rightward
Explicitly control the way that duplicate points will be clustered.
Default method is 2d for 2-D scatterplots, horiz for 1-D scatterplots
where Y location is fixed, and vert for 1-D scatterplots
where X location is fixed.
upward and rightward may be used to string duplicate points upward
or rightward to form little bars. horiz will cluster duplicate points
only horizontally; vert will cluster duplicate points only vertically.
An example of using clustermethod: upward to form rows of little bars,
is
snpmap1
To represent duplicate points using different symbol colors (etc.) see dupsleg.
clusterfact n
May be used when clustering is being done. The clustering offset distance
will be multiplied by this
amount. A value of 1.0 would leave the clustering offsets unchanged,
while 2.0 would spread clustered points out more, and 0.5 would
spread them out less.
clusterdiff f
May be used when clustering is being done. Two values
that are within f of each other will be considered duplicates
eligible for clustering. Default value is 0.01.
clustevery n
With clustering, normally every duplicate point is offset from all
the others,
which may not be effective if there are large numbers of duplicate points.
In order to reduce the clutter, this attribute may be used to offset
only for every nth duplicate encountered.
Example: clustevery: 5 ..would result in a point having 35 duplicates
represented using 7 point marks.
dupsleg yes | no
If yes the symbol color, size, shape, etc. will be controlled by the number of duplicate points counted.
This uses the
legend-driven technique
. Each legend entry must have a tag that is an integer,
and a
symboldetails
entry for details.
Legend entries must be specified in numerical order by tag, from highest to lowest.
As the scatterplot is drawn and duplicate points are detected,
a count of duplicates is maintained.
Then the count is compared against the set of tags (from highest to lowest).
When a tag is found that is <= the duplicate count, that
legend entry is chosen, and the point will be rendered using the symbol
described in that entry.
Example:
dupsleg
symfield
dfield
If specified, the symbol color, size, shape, etc. will be controlled by this data field
using the
legend-driven technique
.
Example:
symfld
symrangefield
dfield
Same as symfield above, except that numeric range comparison is used
when finding the appropriate legend entry, using the
legend-driven technique
Legend tags must be a single numeric value.
Legend entries must be specified in numerical order by tag, from highest to lowest.
Prospective values will be compared against legend entries in the order specified (highest to lowest);
when a legend entry tag is found that is less than or equal to the contents of
the symrangefield data field,
that legend entry is chosen, and the point will be rendered using the symbol
described in that entry.
Example:
symrangefld
select
conditional-expression
May be used to select data rows for inclusion into the scatterplot.
Example: select: @3 = AA
xrange low high
If specified, only data points within the given plottable range in X
will be shown. By default the points will be drawn only if within
the plotting area.
Example: xrange: 0 50
yrange low high
If specified, only data points within the given plottable range in Y
will be shown. By default the points will be drawn only if within
the plotting area.
Example: yrange: 0 50
clickmapurl url template
If generating an
HTML clickmap
, this specifies a url template, and
causes the data points (symbol or character) to be mapped.
This attribute usually contains one or more embedded
data field references
preceded by double at-sign (@@).
See
HTML clickmap
for more details and examples.
Example: clickmapurl: http://abc.com/mycgi?category=@@3
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 data display engine
Copyright Steve Grubb
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