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RTAnalysisManagingData / VariableCalculation

Variable calculation

From v8.5 the way that variables where calculated has changed. In v8.5+ variables are only calculated when they are needed, for example even if “brake pressure” is active in the variable manager, if it is never used then it is not calculated which saves CPU time.

The way memory is allocated to variables has also changed, in that all variables are always available, however they can still be “disabled” in the variable manager which stops them being listed elsewhere is the software.

There are a couple of important options that control how variables are handled:

Under the Data menu -> Analysis options -> Data tab there are a few important options:

The first option is used to control how variables are activated or shown elsewhere in the software. There are 2 alternatives here:

  • manually activated variables. In this case the user is left to decide which variables are on. This gives the most flexibility, but new users might find it confusing.
  • Automatically activate all variables with data. In this case the system detects when a variable has data in when it has the variable is activated, where there is no data then it is deactivated or hidden.

Note that the above schemes are not quite as simple as they first appear. In the simple case they work well, for example if you have an ECU interface that outputs Exhaust temperature then this variable will automatically be come active, otherwise it remains hidden. However there are many more complicated scenarios.

For example some variables calculated by the analysis software do not have any explicit data samples mapped to them, for example:

  • time into lap
  • calculated power
  • simulated speed
  • user defined variables

so in these and many other cases we cannot activate them based on whether they have data. As a partial work around to this issue when you activate automatic variable selection, not only are variables with data activated, some of the most common analysis calculated variables are also activated. These variables are:

  • time
  • lateral, longitudinal and vector acceleration
  • speed
  • position x and position y
  • distance
  • power
  • time slip
  • time slip rate
  • simulated speed
  • simulated time slip
  • simulated time slip rate
  • gear
  • user variables 1 to 5

Note that if you want a different selection of variables (for example time into lap, torque etc etc) then the only option is to use the manual variable selection method.

Although v8.5 can automatically calculate variables only when they are needed, depending on the application this is not always the most desirable behaviour. To cater for different requirements, there are 2 options:

  • Automatically calculate acceleration, distance, and mapping when data is loaded. Typically these variables are nearly always needed, so it makes sense to calculate them immediately rather then delay until you try to use them in the software.
  • Automatically update all variables. This forces everything to be calculated, which means that all the variables are ready for use immediately. For some applications this can be preferable, for example if there are very few variables activeo or for very short data sets, however normally this is not required and slows down the data handling when you load a new run.

In the Variable manager -> options there are also some options:

These option control whether variables are listed in the variable manager only when they have data, or always.

Again, the choice depends on the users preference. Hiding variables that have no data available makes the run manager far neater and quicker to navigate, however it can be confusing if the particular variable that you want to use is not listed. In particular note that in the case that the user wants to active a internally calculated variable that is not one of the “common variables” as listed above, for example “time into lap”. Since this is not a shown it cannot be activated.

Page last modified on November 22, 2013, at 07:55 AM