Welcome to GRAPH-XT > Getting Started > Getting Started with Bubble Plots

Info: A very detailed bubble plot example can be found in the DPlot_example1.prg example program, see SUB Dplot_bub_plot.

A bubble plot lets you chart three variables in two dimensions by varying the size of each data point in a scatter plot based on a third variable. In GRAPH-XT, that third variable is taken from the Y values of a separate curve. The source curve for the bubble amplitudes will not be drawn. GRAPH-XT ignores the X values for the source curve(s); the n’th point of the source curve is used as the bubble amplitude for the n’th point of the selected curve, regardless of whether the X values match up.

The following chapter shows how to create a simple bubble plot like this:

clip0039

Doc_num=FNDplot_doc_new(0) ! create new document

Xmin=0

Xmax=2*PI

Xpoints=50

Xstep=Xmax/Xpoints

Ymin=0

Ymax=2*PI

Ypoints=100

Ystep=Ymax/Ypoints

ALLOCATE REAL Datxy(1:Xpoints,1:2) ! 2-dimensional array

ALLOCATE REAL Datxy2(1:Xpoints,1:2) ! used for z values for bubble plot

Xi=BASE(Datxy,1)

FOR X=Xmin TO Xmax STEP Xstep

Datxy(Xi,1)=COS(X) ! x value 1st curve

Datxy(Xi,2)=SIN(X) ! y value 1st curve

Datxy2(Xi,1)=COS(X) ! x value 2nd curve

! y value 2nd curve (used for symbol size for first curve = bubble plot)

Datxy2(Xi,2)=ABS(SIN(X))

IF Xi<Xpoints THEN Xi=Xi+1

NEXT X

! transfer all data points to DPlot curve 1, line type 1

Dummy=FNDplot_xyz_data(Doc_num,Datxy(*),0,0,1,"x=cos(t), y=sin(t); {0<t<2*PI}",1)

! transfer all data points to DPlot curve 2, line type 1

Dummy=FNDplot_xyz_data(Doc_num,Datxy2(*),0,0,2,"x=cos(t), y=abs(y); {0<t<2*PI}",1)

DEALLOCATE Datxy(*)

CALL Dplot_scr_size(Dw,Dh) ! get screen size

Sl=100 ! size of symbols for low values

Sh=300 ! size of symbols for high values

IF Dw<800 THEN

Sl=60 ! looks better on small displays

Sh=180 ! looks better on small displays

END IF

! The following command creates the bubble plot.

! Sets bubble plot parameters for the curve with 1-based index curve.

! The symbol type is specified by the symbol parameter (see all

! available symbol types in the description of the SymbolType command).

! The symbol size will be based on the Y values of the curve with 1-based

! index source. The source curve will not be drawn.

! The X values for the source curve are ignored.

Dummy=FNDplot_send_cmd("[Bubbles(1,288,2,"&VAL$(Sl)&","&VAL$(Sh)&",0xFF0000,0x0000FF)]")

! legend text and style for curve

Dummy=FNDplot_send_cmd("[Legend(1,""x=sin(2*t), y=sin(5*t) {0<t<2*PI}"")]")

Dummy=FNDplot_send_cmd("[NumberFormat(0,8)]") ! x axis = fractions of PI

Dummy=FNDplot_send_cmd("[ManualScale(-1.1,-1.20,1.1,1.20)]") ! manual scale of y axis

! show the diagram, 100% screen size

CALL Dplot_show(Doc_num)

Dummy=FNDplot_doc_close(Doc_num) ! close the document