xset cosmo ⚬ Entries

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xset ⚬ˣˢᵖᵉᶜ｜docu｜1st｜20251021185654-00-⌔

xset

xset

set variables for XSPEC models

Modify a number of XSPEC internal switches.

Syntax: xset [abund |cosmo |delta |mdatadir |method |seed |statistic |usechainrule |weight |xsect |<string_name>] [|<string_value>]

The arguments abund, cosmo, method, statistic, weight, and xsect just run the appropriate XSPEC commands. mdatadir changes the directory in which XSPEC searches for model data files. You probably don’t want to change this. The seed option requires an integer argument, which will then be used to immediately re-seed and re-initialize XSPEC’s random-number generator.

The delta option is for setting fit delta values (see the newpar command) which are proportional to the current parameter value rather than fixed. For example,

XSPEC12> xset delta .15

will set each parameter fit delta to.15 ﹡ parVal. To turn proportional deltas off and restore the original fixed deltas, set delta to a negative value or 0.0. The current proportional delta setting can be seen with show control.

The usechainrule option can be used to switch between the fast (usechainrule yes) and slow (usechainrule no) options when calculating the derivatives of the fit statistic.

The <string_name> option can be used to pass string values to models. XSPEC maintains a database of <string_name>, <string_value> pairs created using this command. Individual model functions can then access this database. Note that xset does no checking on whether the <string_name> is used by any model so spelling errors will not be trapped.

To access the <string_name>, <string_value> database from within a model function use the fortran function fgmstr. This is defined as character﹡128 and takes a single argument, the string name as a character﹡128. If the <string_name> has not been set then a blank string will be returned.

The current <string_name> options, models to which they apply and brief descriptions are given in the following table:

📊 ➺

Examples:

XSPEC12> xset NEIAPECROOT 2.0
  // Set the NEIAPECROOT variable to 2.0
XSPEC12> xset 
  // List the current string variables
XSPEC12> xset apecroot /foo/bar/apec_v1.01
  // Set the APECROOT variable
XSPEC12> xset seed 1515151
  // Re-initialize the pseudo random-number generator
  // with the seed value 1515151

Printed 2026-06-28.

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