Formula
Input Variables
Operators, Functions and
Constants
Output Section
You can calculate parameters using a full range of usual mathematical expressions and functions by simply typing the required formulae into the text box.
You can use as inputs to the formula the results from the analysis stage, previous calculations you have defined in the calculation list and also Subject Measurements variables which appear in the MP file associated with the trial.
The usual options are given for the presentation of the result into the trial or text file.
The formula is entered in text format in the edit box. You should just enter the definition of the value you want to calculate - there is no need to write the new name or the equals sign.
The formula is not case sensitive.
Spaces are optional in the formula. Use them freely to keep your formulae easy to understand.
Input Variables
Analysis Parameters
These can be used as input to the formula, and are referred to by the name (description) which you applied when you defined the analyzer.
Subject Measurement
Any subject measurement can be entered into the formula. The name should be specified as it appears in the Subject Measurements dialog in Workstation, or as the variable appears in the MP text file.
Calculation Variables
Any previously calculated variable can be used as an input. Use the name you gave when defining the calculation. Calculated variables used as input must appear earlier in the Calculation List.
Context
You need to specify the context for each of the input variables in your formula by using the name of that context, i.e. Left, Right or General.
The context must precede the name of the variable.
Operators, Functions and Constants
The mathematical expressions you can use in the formula can be listed by pressing the Keywords button.
Round brackets "()" can also be used to enforce order of evaluation.
Name
You can type in any name you like for the calculation you are making. This description appears in the output so you can tell what the calculation refers to. There is no other significance attached to this.
Units
Like the Name, you can type whatever you like here, and it will appear in the output. It does not alter the calculation. There is a drop down list of common alternatives to choose from.
Context
For each calculation, you have the option to refer the result to a particular Context, which affects how the result is shown in the text file or in Polygon. Normally the context will be the same as that of the analysis parameters you are calculating from, but this may not be true, depending on what it is you are calculating.
Don't output (only use for calculations)
The default setting is that the result of any calculation should be output (according to the settings). This can be overridden by checking the "Don't Output" option.
This option allows you to generate parameters which are used in a subsequent calculation stage without cluttering the output with unnecessary data.