Documentation

Tree structure to be used with Symbolic Regression algorithms. This structure is a fixed point of a n-ary tree.

Supported functions

Supported operators

create a tree with a single node representing a parameter

create a tree with a single node representing a variable

create a tree with a single node representing a constant value

Arity of the current node

Get the children of a node. Returns an empty list in case of a leaf node.

>>> map showExpr . getChildren $ "x0" + 2
["x0", 2]

Count the number of nodes in a tree.

>>> countNodes $ "x0" + 2
3

Count the number of Var nodes

>>> countVarNodes $ "x0" + 2 * ("x0" - sin "x1")
3

Count the number of const nodes

>>> countConsts $ "x0"* 2 + 3 * sin "x0"
2

Count the number of Param nodes

>>> countParams $ "x0" + "t0" * sin ("t1" + "x1") - "t0"
3

Count the occurrences of variable indexed as ix

>>> countOccurrences 0 $ "x0"* 2 + 3 * sin "x0" + "x1"
2

counts the number of unique tokens

>>> countUniqueTokens $ "x0" + ("x1" * "x0" - sin ("x0" ** 2))
8

return the number of unique variables

>>> numberOfVars $ "x0" + 2 * ("x0" - sin "x1")
2

returns the integer constants. We assume an integer constant as those values in which `floor x == ceiling x`.

>>> getIntConsts $ "x0" + 2 * "x1" ** 3 - 3.14
[2.0,3.0]

Relabel the parameters indices incrementaly starting from 0

>>> showExpr . relabelParams $ "x0" + "t0" * sin ("t1" + "x1") - "t0"
"x0" + "t0" * sin ("t1" + "x1") - "t2" 

Change constant values to a parameter, returning the changed tree and a list of parameter values

>>> snd . constsToParam $ "x0" * 2 + 3.14 * sin (5 * "x1")
[2.0,3.14,5.0]

Same as constsToParam but does not change constant values that can be converted to integer without loss of precision

>>> snd . floatConstsToParam $ "x0" * 2 + 3.14 * sin (5 * "x1")
[3.14]

Convert the parameters into constants in the tree

>>> showExpr . paramsToConst [1.1, 2.2, 3.3] $ "x0" + "t0" * sin ("t1" * "x0" - "t2")
x0 + 1.1 * sin(2.2 * x0 - 3.3)