Creating a Triplot
Petroleum geochemistry utilises triplots, or ternary diagrams, during interpretation to plot data for three related properties simultaneously.
Version: 1.7.2+ (Aug 2017)
Usage: Graph --> New Graph --> New triplot...
How to use in practice
The plot creation dialogue for a triplot requires 3 properties for creation:
- Property 1 - A numeric geochemical property with associated indicator, unit and ratio where appropriate, which will correlate with the left hand side red axis.
- Property 2 - A numeric geochemical property with associated indicator, unit and ratio where appropriate, which will correlate with the base green axis
- Property 3 - A numeric geochemical property with associated indicator, unit and ratio where appropriate, which will correlate with the right hand side blue axis.
Properties are selected using the standard property selector present throughout the software.
Once created axis ranges can be managed through the Exploration tab in Graph Manager. The constraints in the triplot mean that editing the axes is different from other graphs, because changing just one axis will affect at least one other axis. There are two main options here - you can zoom to the data / the full simplex (all properties 0-100%), or manually edit the minimum percentages on each axis. For example changing the minimum for property 1 (red axis) to 10% implies that the other two axes can at most show 90%. If you find you get lost in the zoom, using the zoom to data / simplex options are very useful.
Properties cannot be edited post creation, as it is unlikely that when changing one of three selected properties a valid triplot would result, making it more logical to create the new triplot from the new triplot creation dialogue, however you can edit the names given to each axis (from v188.8.131.52).
The software will automatically normalise the 3 chosen properties relative to their sum for each sample to be plotted. Note this normalisation is necessary to ensure points always plot in the triangular simplex of the plot. The simplex here refers to the part of 2D space in which the 3 axes produce a valid position, that is where x+y+z = 100%.
Graph interpretative layers are covered in another section of the user guide.
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