Inputing and Editing Graph Data

All the commands concerned with inputing data and plotting graphs are prefixed by the letters "XY". Data to be plotted are read into buffers within QCL using one of the following commands

qcl>XYFMT GRP_DATAF,GRP_XCOL,GRP_EXCOL,GRP_YCOL,GRP_EYCOL,
           GRP_STARTLINE,GRP_ENDLINE

qcl>XYHDS GRP_XMODE,GRP_XNAM1,GRP_XNAM2,GRP_YMODE,GRP_YNAM1,GRP_YNAM2

qcl>XYHXS GRP_DATYPE,GRP_ISEL,GRP_IDLO,GRP_IDHI

These commands must be used to access the data before plotting. They also set defaults for user coordinate mapping and graph labels etc. so that drawing a complete graph is made easy.

XYFMT

XYFMT will access data from a formatted file which contains columns of numbers. GRP_XCOL specifies the column which contains the X coordinates, GRP_EXCOL is the column for any errors on X. Similarly, Y values are specified by columns GRP_YCOL and GRP_EYCOL. If GRP_XCOL=0 then a start X value and X-increment GRP_XLO and GRP_XSAM will be requested. If the other column values are set equal to zero values for the appropriate data will not be read. GRP_STARTLINE and GRP_ENDLINE specify the line numbers to be accessed from the file. If a format error occurs during a read then that line of the file will be skipped.

XYHDS

The command XYHDS is provided to gain generalised access data from a HDS file. The structure object which contains the data must be specified by assigning the symbolic name HDS_NODE before using this command. If the data required are objects at the top level of the container file then

HDS_NODE=<filename>

HDS_NODE='joke.sdf%node1.node2'

The parameters GRP_XMODE and GRP_YMODE are used to describe how the data object names are to be used to generate the XY data and error values. The access modes available are as follows:

In each case the range of J is determined by the total number of elements in YNAM1. Modes 1 and 2 are therefore not available for generating Y data and error values. The total number of elements associated with GRP_XNAM1, GRP_XNAM2, GRP_YNAM1 and GRP_YNAM2 must be compatible with the modes specified and with each other. Hence if GRP_XMODE=1 then GRP_XNAM1 and GRP_XNAM2 must be scalars or single cells, e.g. GRP_XNAM1='TBASE' and GRP_XNAM2='TSAMPLE(3)'. If it is required to plot a limited slice of a large array then the limits of the slice can be specified in the object name, e.g. GRP_YNAM1='DATA(3:55)', GRP_YNAM2='ERROR(3,3:55)'.

XYHXS

The command XYHXS provides access to the specialised 3-dimensional time series and spectral files within the Leicester Data Analysis System. Its use is thus restricted to files which conform to the TIME * PHA * IDENT structure. The parameter GRP_DATYPE (= TIME or = PHA) elects light curve or spectral data, GRP_ISEL specifies which element of the TIME dimension (for spectral data) or PHA dimension (for TIME data) is required (usually GRP_ISEL=1). GRP_IDLO and GRP_IDHI select the element, or range of elements, of the IDENT dimension required. If a range is specified, the data are automatically summed before insertion into the plot buffers.

Editing data

Once the above access commands have been used there will be GRP_NP data points set in the internal XY buffers. The command

qcl>XYSET GRP_NPOINT,GRP_XP,GRP_XEP,GRP_YP,GRP_YEP

can be used to modify the contents for the data point with subscript GRP_NPOINT. GRP_XP and GRP_XEP are the new X value and associated error, GRP_YP and GRP_YEP are the equivalent new Y values.

The parameters GRP_XP, GRP_XEP, GRP_YP, GRP_YEP can be set equal to the values for a given data subscript GRP_NPOINT using the command

qcl>XYVAL GRP_NPOINT

Hence the commands XYSET and XYVAL provide a direct two-way path between the data buffers and QCL parameters.