Note that in RGeostats, the categories (also called lithotype, facies, ...) are coded by using integers between 1 and the number of categories. The rules involve one or two Gaussian Random Functions (GRFs) and can be created according to two ways:
By using an interface with the function
- Code: Select all
rule.input
or with the command line by using
- Code: Select all
rule.create
1) A simple rule
We start this tutorial by showing how to create the simplest (non trivial) rule: a rule involving 1 GRF to model 2 facies.
The command
- Code: Select all
rule=rule.input()
provides an interface as follows (the answers are indicated in red and explanations are given hereafter):
Choose the Rule Definition mode
0 : Standard definition of GRF
1 : Definition of one GRF with Shift
2 : Definition of one GRF with Shadow
Rule Definition mode [0,2] : 0
Correlation between the two GRFs (Def=0.000000) [0.000000,1.000000] : 0
Enter the Lithotype Rule (recursively)
Use 'F' (Facies), 'S' (Threshold Y1), 'T' (Threshold Y2) or 'stop'
Choice of node 'main' [F,S,T] : S
Use 'F' (Facies), 'S' (Threshold Y1), 'T' (Threshold Y2) or 'stop'
Choice of node 'S1 [Low]' [F,S,T] : F
Enter the Facies value [1,NA] : 1
Use 'F' (Facies), 'S' (Threshold Y1), 'T' (Threshold Y2) or 'stop'
Choice of node 'S1 [Sup]' [F,S,T] : F
Enter the Facies value [1,NA] : 2
The first answer will always be 0 in this tutorial since the other modes should become obsolete in a future version.
The second one indicates the correlation coefficient between the two GRFs (i.e the value of the cross-covariance at distance 0).
This value has to be consistent with the bivariate spatial model.
However, this is currently irrelevant since we are creating a rule for only one GRF (we have answered 0)
After that, we answer S which indicates that we want to divide the current window in two.
Then we have to answer how to fill the left part of the window. We have answered F which indicates that we want to fill it with a facies and then 1 to say that it is the first one.
Then we are asked to say how we want to fill the right window. We have answered F then 2 to fill it with the facies 2.
To obtain the same result as previously without any interface, we can use:
- Code: Select all
rule=rule.create(c("S","F1","F2"))
plot(rule)
Try also:
- Code: Select all
rule=rule.create(c("S","F2","F1"))
plot(rule)