NAME

express -- Validate the constraint expressions in a DB table.

USAGE

express db_intab

DESCRIPTION

This task evaluates all the constraint expressions in a component DataBase table, and outputs warning messages for each constraint that cannot be evaluated. This task is meant as a quick way to validate the constraint expressions before invoking a fit process with the "autospec" task, possibly in background mode or with a script.

Errors that are trapped are reported to STDOUT, although this output may of course be redirected to a file. If "verbose=yes" then each expression evaluation will be written out, whether there is an error or not. The evaluated expressions will be converted for output to the flux or dispersion units specified by the "flux_unit" or "dsprsn_unit" parameters, respectively.

Errors can occur either because the syntax of the contraint expression is incorrect, or because the expression references a non-existant component. The expressions can be corrected either with a table editor or, preferably, with the "Manage Components" panel in the interactive "vuespec" task.

PARAMETERS

db_intab = "" [string]

DataBase table from which the component definitions, parameter values, and constraint expressions will be drawn.

(flux_unit = "FLAMDA") [string]

System of flux units for the evaluated constraint expressions. The possible choices are: "PHOTLAM|PHOTNU|FLAMDA|FNU|JY|MJY" and are adopted from the STSDAS "synphot" package. Briefly, PHOTLAM and PHOTNU both express brightness in units of equivalent photons/cm**2/s: the former per unit wavelength (Angstroms), and the latter per unit frequency (Hz). FLAMDA and FNU both express brightness in units of ergs/cm**2/s: again per unit Ang or per unit Hz, respectively. JY and MJY are Janskys and milli-Janskys, respectively.

(dsprsn_unit = "ANG") [string]

Dispersion units for the evaluated constraint expressions. The possible choices are: "ANG|NM|MICRON|CM|HZ|MHZ|GHZ|EV|KEV|MEV". The latter three are expressed as the frequency of a photon with the equivalent energy in electron volts.

(verbose = no) [bool]

Print the evaluation of all the constraint expressions? The default is to print out only those expressions that result in an error.

EXAMPLES

1. Evaluate the parameter constraint expressions stored in the table "NGC6543_db.tab".

   cl> express NGC6543_db.tab

REFERENCES

This package was written by J.D. Eisenhammer, S.J. Hulbert, Z.G. Levay, and R.A. Shaw. Support for this software development was provided by the Astrophysics Data Program through NASA grant NAG5-31859 to STScI.

SEE ALSO

autospec, spiopars, vuespec