SPSS® 12.0 Command Syntax Reference

760 IGRAPH
The INTERPOLATE keyword determines how the lines connecting the points are drawn.
Options include:
STRAIGHT Straight lines.
LSTEP A horizontal line extends from each data point. A vertical riser connects
the line to the next data point.
CSTEP Each data point is centered on a horizontal line that extends half of
the distance between consecutive points. Vertical risers connect the
line to the next horizontal line.
RSTEP A horizontal line terminates at each data point. A vertical riser
extends from each data point, connecting to the next horizontal line.
LJUMP A horizontal line extends from each data point. No vertical risers
connect the lines to the points.
RJUMP A horizontal line terminates at each data point. No vertical risers
connect the points to the next horizontal line.
CJUMP A horizontal line is centered at each data point, extending half of the
distance between consecutive points. No vertical risers connect the
lines.
SPLINE Connects data points with a cubic spline.
LAGRANGE3 Connects data points with third-order Lagrange interpolations, in
which a third-order polynomial is fit to the nearest four points.
LAGRANGE5 Connects data points with fifth-order Lagrange interpolations, in
which a fifth-order polynomial is fit to the nearest six points.
Example
IGRAPH
/X1=VAR(volume95) TYPE=CATEGORICAL
/Y=VAR(sales96) TYPE=SCALE
/COLOR=VAR(volume94) TYPE=CATEGORICAL
/COORDINATE=VERTICAL
/LINE (MEAN) STYLE=LINE DROPLINE=ON LABEL VAL
INTERPOLATE=STRAIGHT BREAK=MISSING.
• LINE creates a line chart. The lines represent the mean value of sales96 for each category
of volume95.
• The chart contains a line for each category of volume94, with droplines connecting the
lines at each category of volume95.
• LABEL labels the lines with the mean sales96 value for each category of volume95.
• INTERPOLATE specifies that straight lines connect the mean sales96 values across the
volume95 categories.
• BREAK indicates that the lines will break at any missing values.