[AstroPy] Composite models or input arrays
eric.emsellem at eso.org
Wed Aug 26 03:19:48 EDT 2015
> What you want is to use a model set. This is a still poorly understood feature
> and I'm open to suggestions for how to make this more "obvious" (part of the
> difficulty in that has been supporting a multitude of different use cases
> simultaneously). You can read about that here:
> In short, a*model set* is what you want if you want to represent a collection
> of independent instances of the same model with different parameters.
wahh... quite powerful. Sorry to have missed that part of the
documentation. This is really great and solves quite a number of issues
I had in mind.
At the end, I need to choose between (the examples below would need
extra lines/variables, but this is I hope explicit enough):
1- for i in range(N) : ModelT += MyModel(par1= , par2= , par3= )
(each Model being the same MyModel but with different instances provided
as going through the for loop)
(I could also use model_instance = ModelT(....) to set the parameters
after the fact as you suggested)
2- ModelT = MyModel(par1=[...], par2=[...], par3=[...], n_models=N)
The second option (model set) seems quite natural. It also has the
advantages to have both the "parameters" as an array including all
parameters (2d array), and each individual parameter (par1, par2, par3)
as an individual array (I checked that 'parameters' and e.g., 'par1' are
views of each others so when I modify one the other one is also
modified, via a setter/view I guess -> great!).
=> However, I don't know how to slice the model set then (e.g., compute
ModelT(x) just using e.g., the 1st and 3rd model of that set). By the
way, with a compound model, I guess I cannot do ModelT[[0,2]] to access
only model 1 and 3.
=> More generally, and as mentioned in a previous email, I would also
like to be able to add more instances of MyModel, or remove some of them.
With Option 1, I can just do ModelT = ModelT + MyModel(par1=, par2=,
par3=) to add one
ModelT = ModelT + ModelT to remove one (as you suggested)
Could you do that easily with a model set? (1- compute the output on a
slice of the models, a selected subset, and later on add or even remove
completely one of the models in the model set?).
Anyways, this is quite amazing. I was a bit dubious when I started to
examine the possibility to use the astropy.modeling. I am more than
convinced now and this is going well beyond what I had imagined (and I
haven't seen everything yet by far). Thanks so much for these developments!
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