IGI’s software has a powerful equation system that computes derived values automatically when input properties are provided. But what are input properties and whare derived values?
Let’s take everyone’s favourite pristane/phytane ratio as an example. There’s no prizes for guessing both pristane (Pr) and phytane (Ph) are the required input properties for the derived value of the pristane/phytane (Pr/Ph) ratio. Without pristane or phytane you cannot calculate the ratio, but imagine importing the following table into p:IGI+:
| Sample name | Pr | Ph | Pr/Ph |
| Partial | 1 | 2 | |
| Full | 1 | 2 | 0.50 |
| Incorrect | 1 | 2 | 0.30 |
| Given | 0.50 |
Which results in:
The first sample “Partial” only has the inputs, Pr and Ph, allowing p:IGI+ to calculate the Pr/Ph ratio. While the second sample “Full” has all the inputs and pristane/phytane itself, in this scenario p:IGI+ still calculates Pr/Ph. Why?
The third example “Incorrect” answers that question. Here we have the same inputs but Pr/Ph is wrongly recorded as 0.3. Once again, p:IGI+ calculates pristane/phytane overwriting the value given on import. We calculate equations wherever possible to ensure the values given are correct and consistent.
The first three samples all have the same inputs and therefore all have the same derived value. The eagle-eyed amongst you will spot that p:IGI+ uses a green italicized font to denote when a value has been calculated.
Lastly, what happens when some or all of the inputs to an equation aren’t given? The last sample “Given” only has a value for Pr/Ph. In this scenario all the software can do is use the value being imported and trust it is correct. To show the value has been user given, the standard black font is used.
There are hundreds of equations in IGI’s data model, some can even be calculated even when not all of the inputs are present. p:IGI+ and Metis’ equation system works behind the scenes to give you confidence the values being shown are as consistent and correct as possible.
