Summary of Commands

The following is a list of the commands available in XSPEC, together with a brief description of the purpose of each. The commands have been categorized under six headings: Control, Data, Fit, Model, Plot, Script, and Setting. The Control commands contain the interface with the operating system: they cause commands to be executed, or user input written to disk, or control how much is output. The Data commands manipulate the data being analyzed, by reading data into the program or replacing spectra or their ancillary detector, background, correction, or efficiency (auxiliary response) arrays. Additionally data commands control the channels under analysis. The fit commands invoke the fitting routines, modify their behavior by interchanging fitting algorithms or statistics in use, fixing parameters, or perform statistical testing. The Model commands create or manipulate the model, adding or editing components, modifying parameters, or alternatively performing analytical calculations from a model. The Plot commands deal with all aspects of plotting. The scripts are auto-loaded Tcl scripts that can be used in the same ways as commands. Finally the Setting commands sets variables that affect theoretical models.

Command	Category	Description
abund	Setting	Set the abundance table.
addcomp	Model	Add a component to the model.
addline	Model	Add lines to a model
arf	Data	Read an auxiliary response file.
autosave	Control	Periodically save the XSPEC status.
backgrnd	Data	Reset the files to be used for background subtraction.
bayes	Fit	Set up for Bayesian inference.
chain	Fit	Run a Monte Carlo Markov Chain.
chatter	Control	Control the verbosity of XSPEC.
corfile	Data	Reset the files to be used for background correction.
cornorm	Data	Reset the normalization to be used in correcting the background.
cosmo	Setting	Set H₀, q₀, and
cpd	Plot	Alias for setplot device.
data	Data	Input one or more PHA data files.
delcomp	Model	Delete a component from the model.
diagrsp	Data	Diagonalize the current response for an ideal response.
dummyrsp	Model	Create a dummy response, covering a given energy range.
editmod	Model	Add, delete, or replace one component in the model.
energies	Model	Specify new energy binning for model fluxes.
eqwidth	Model	Calculate a model component’s equivalent width.
error (rerror)	Fit	Determine a single parameter confidence region. rerror is for response parameters.
exec	Control	Execute a shell command from within XSPEC.
exit	Control	Wind up any hardcopy plots and exit from XSPEC.
extend	Model	This is now obsolete. See energies command.
fakeit	Data	Produce simulated data files for sensitivity studies.
fit	Fit	Find the best fit model parameters.
flux	Model	Calculate the current model's flux over an energy range.
freeze (rfreeze)	Fit	Do not allow a model parameter to vary during the fit. rfreeze is for response parameters.
ftest	Fit	Calculate the F-statistic between two model fits
gain	Model	Perform a simple modification of the response gain.
goodness	Fit	Monte Carlo calculation of goodness-of-fit.
hardcopy	Plot	Spool the current plot to the printer.
help	Control	Obtain help on XSPEC commands.
identify	Model	List possible lines in the specified energy range.
ignore	Data	Ignore a range of PHA channels in future fit operations.
initpackage	Model	Compile, build, and initialize a package of local models.
iplot	Plot	As plot command but interactive using PLT.
lmod	Model	Load a package of local models.
log	Control	Open the log file to save output.
lrt	Script	Likelihood ratio test between two models.
lumin	Model	Calculate the current model's luminosity over a given rest frame energy range and redshift.
margin	Fit	MCMC probability distribution.
mdefine	Model	Define a simple model using an arithmetic expression.
method	Setting	Set the minimization method.
model (rmodel)	Model	Define the model to be used when fitting the data.
modid	Model	Guess line IDs in the model.
multifake	Script	Perform many iterations of fakeit and save the results in a FITS file.
newpar (rnewpar)	Model	Modify the model parameters. rnewpar is for response parameters
notice	Data	Restore a range of PHA channels for future operations.
parallel	Control	Enable parallel processing for particular tasks in XSPEC.
plot	Plot	Plot various information on the current plot device.
query	Control	Switch on/off prompt to continue fitting.
quit	Control	An alias for exit
renorm	Fit	Adjust the model norms, and/or control automatic renorming.
rescalecov	Script	Rescale the covariance matrix used in the proposal chain command.
response	Data	Reset the files used to determine the detector responses.
save	Control	Save aspects of the current state to a command file.
script	Control	Open the script file to save all commands input.
setplot	Plot	Modify the plot device and other values used by the plot routines.
show	Control	Display current file and model information.
simftest	Script	Generate simulated datasets to estimate the F-test probability for adding a model component.
source	Control	Execute a script file.
statistic	Setting	Change the fit statistic in use.
steppar	Fit	Step through a range of parameter values; perform a fit at each step.
syscall	Control	Run a shell command.
systematic	Model	Set the model systematic error.
tclout	Control	write xspec data to a tcl variable
tcloutr	Control	tclout with return value
thaw (rthaw)	Fit	Allow a model parameter to vary during the fit. rthaw is for response parameters
time	Control	Display elapsed time and other statistical information.
uncertain	Fit	Alias for error
untie (runtie)	Model	Untie linked parameters. runtie is for response parameters.
version	Control	Print XSPEC version and build date/time
weight	Fit	Change the weighting function used for chi-squared fits.
writefits	Script	Write information about the current fit and errors to a FITS file.
xsect	Setting	Change the photoelectric absorption cross-sections in use.
xset	Setting	Modify a number of XSPEC internal switches