Building signals


Building signals in LTPDA can be done in various ways. Perhaps you already have data in a text file, or you have a formula for a particular time-series. These can all be accommodated by the AO constructor.

Another useful way to build template signals is by using so-called 'built-in models'. These built-in models serve as kind-of user-defined constructors. They typicall output objects of a particular type, with the exact details of the object being governed by a few configuration parameters. For example, you've already used a built-in model to build a particular kind of ssm object -- the LPF model. We also have built-in models for some of the signal templates indended for use in some of the LPF system identification experiments.

If you launch the LTPDA model browser, you can browse the various built-in models available to LTPDA on your system. To launch the browser, do:

  >> LTPDAModelBrowser    
You can also request a textual list of the available models for a particular LTPDA user class by doing, for example,
  >> ao.getBuiltInModels

Building signals from AO built-in model

The battery of signals prescribed in S2-UTN-TN-3045 for the first system identification experiment can be built using the following command:

  >> sig = ao(plist('built-in', 'signals_3045_1_1'));
If you plot this AO you should see a plot like this:
There are a number of ao built-in models included in the LPF_DA_Module which reproduce the signals for the TN-3045 experiments. All 6 of these models have a single configurable parameter. To see the help/description for this model, either use the model browser, or from the terminal do:
  >> help ao_model_signals_3045_1_1
This pattern is always the same in LTPDA, to get help for any built-in model, you need to know its class, then just do:
  >> help [class]_model_[model name]
The help usually includes a short description of the model and a link called "Model Information". If you click on that you will see a window which gives more information about the model and the parameters you can configure at build-time. For example, for the model we built above, you can also specify the gap you want to have between each of the 7 finite duration sine-waves. The duration of the sine-waves is specified by the experiment and so is not a parameter. To change the gap between all signals to 1000s, build the model like this:
  >> sig = ao(plist('built-in', 'signals_3045_1_1', 'gaps', 1000));

©LTP Team