As an EasyLanguage Engineer at TradeStation and as a Specialist now, I have had frequent requests to capture and test the plotted signals of EasyLanguage Indicators that clients purchase from other 3rd parties.
Ultimately in the coding world, the question is not can we, but is it worth the effort. TradeStation does not yet expose values of other indicators through a class structure, as with the AccountsProvider and PriceSeriesProvider components in the 9.0 platform. So determining plot values of a protected indicator would be very difficult, unless the indicator writes those values to accessible memory, to files or exposes the values through alerts.
The best way to gain access to indicator values would be for the 3rd-party developer to provide them through an EasyLanguage function. Then the indicator outputs could be used by the client however they like, in their own custom indicator or strategy. In a strategy they could back-test for effectiveness in historical trade simulations.
Unfortunately 3rd-party providers of trading indicators rarely if ever provide the signals through functions, or in strategies. Generally they sell an indicator and an education on using it. But before moving forward with any 3rd-party “tradable” indications, if there is no function or strategy with which you can test the signals you should ask yourself why.
A 3rd party may rightly say that their indicator is for real time only, is multi-asset, or is otherwise a system that cannot be well back-tested with an EasyLanguage strategy. Whatever is said, there is always a way, even if it is only by forward-testing. And if the 3rd-party cannot provide audited results that at minimum FINRA would approve, be very careful.
I have seen countless systems where they show pretty pictures and neat software. They promise that numerous PhDs and supercomputers have been put to task. They have Wall Street professionals on staff, etc. All of that is meaningless and is actually greater evidence of a confidence scheme, than of a truly professional trading system. If they can’t support performance projections or give you a way to test their system independently, stay away!