Drawing Graphs

There are a set of XY... commands to do the graph plotting. Commands prefixed by "XYA" provided mapping if a sensible mapping is not already set and will draw axes and labels. On the other hand commands prefixed by "XY_" use the mapping set without change and will not draw any axes or labels. The "XYA" commands are therefore used to produce an initial complete graph while the "XY_" commands are most useful for adding to an existing plot. The parameters GRP_ILO and GRP_IHI define the range of subscripts to be plotted from the data buffers. If they are not set then the complete range 1 to GRP_NP will be used.

qcl>XYACUR GRP_IDASH,GRP_ILO,GRP_IHI

This command produces a curve by joining the points with straight lines using a dashed line pattern specified by GRP_IDASH (see join for more information about GRP_IDASH). Similarly the following command plots a line histogram.

qcl>XYAHIS GRP_IDASH,GRP_ILO,GRP_IHI

The command

qcl>XYASYM GRP_MINDEX,GRP_MSIZE,GRP_ILO,GRP_IHI

will plot the specified marker GRP_MINDEX of size GRP_SIZE at the specified points.

The two following commands are used to plot data points with errors.

qcl>XYABAR GRP_ILO,GRP_IHI
         
qcl>XYADIA GRP_ILO,GRP_IHI

XYABAR will plot error bars and XYADIA will plot error diamonds.

All these graph plotting commands use the Y error values in a special way. If the Y error is negative then it is assumed there is a gap in the data and the point is not included in the plot.

If logarithmic mapping is used then a check is made to prevent illegal negative or zero values and any points falling outside the mapped area are avoided.

Finally there is a rather different XY command for plotting contour maps from XY data.

qcl>XYACON GRP_ILO,GRP_IHI

This command will plot a contour map of the X error set (the X error values are used as a Z height at each of the XY points specified). For example the X error values might be set equal to the minimum chi-squared achieved when fitting a model using the parameters X and Y. XYACON would then produce a contour plot of the chi-squared surface for a mapped region of the parameters X and Y.

All "XYA" commands have an "XY_" equivalent as follows

qcl>XY_CUR GRP_IDASH,GRP_ILO,GRP_IHI
qcl>XY_HIS GRP_IDASH,GRP_ILO,GRP_IHI
qcl>XY_BAR GRP_ILO,GRP_IHI
qcl>XY_DIA GRP_ILO,GRP_IHI
qcl>XY_SYM GRP_MINDEX,GRP_MSIZE,GRP_ILO,GRP_IHI
qcl>XY_CON GRP_ILO,GRP_IHI