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A.2 fit

fit is the task which performs the actual fitting of observed data to model spectra. The main inputs are a set of observations supplied as a .yobs file, and a set of model data supplied as a .ymod file or in one of the other formats described in Section 4. Some of the other parameters describe how the fitting will be done, and some specify what form the result will be output in.

See Section 3.3 for some more discussion and examples.

Usage: fit [-help] [-debug]
bestfits = <out-table>
Destination filename for a table containing the fitting results. This will be a table with one row for each observation giving the observation details and the details of the model which fits it best, along with the goodness-of-fit score and scaling factor if appropriate. The format of the table is given by the bestfitsfmt parameter.
bestfitsfmt = <out-format>
Table format for bestfits table. Must be one of the permitted STILTS formats such as votable, fits, ascii, text, csv, ... See SUN/256 for a full list.

[Default: (auto)]

fitcalc = chi2|poisson|unscaled
Determines how the goodness of fit score will be calculated.
  • chi2: chi squared using value errors
  • poisson: chi squared using Poisson errors
  • unscaled: absolute root mean squared distance

[Default: chi2]

gui = true|false
If true a window will be displayed plotting the observations and best fit model curves.

[Default: true]

model = <model-file>
File containing the models used for fitting. This will typically be a ymodel file but may be in some other format. The format is given by the modelfmt parameter. Multiple model files (in the same format) may be specified by giving this parameter multiple times.
modelfmt = ymodel|galaxev|starburst99|svotar|sideways-vot
Defines the format of the file given by the model parameter. See Section 4 for a list of known formats.

[Default: ymodel]

obs = <obs-file>
File containing the observations to be fitted against. This must be in yobs format.
scale = true|false
Whether to scale model curves by a multiplicative constant to achieve the best fit. If true, each model curve will be scaled by whatever factor gives the best fit, otherwise its absolute amplitude will be used.

[Default: true]

smoother = square|point
Describes how model curves will be sampled over the width of each observation point for the observations listed in the obs parameter. The options are currently
  • square: the model curve will be uniformly averaged over the width of the observation
  • point: a linear interpolation of the model curve will be taken at the central point of the observation

[Default: square]

summary = <out-file>
Gives the destination file for summary output. This is just a list of the best fit model for each observation. By default, it is written to standard output ("-"), but it can be sent to a file by giving its name here.

[Default: -]

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Yafit - Yet Another Fitting Tool
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