Modeling > Modeling reference > Eureqa advanced tuning > Building blocks reference

Building blocks reference¶

This page provides the definitions and usage of all building blocks available to Eureqa models. To access further information about building block configuration, click the Documentation link provided in any Eureqa model blueprint (found in the upper right corner of any building block under the Advanced Tuning tab).

Arithmetic¶

Building Block	Definition	Usage
Addition	Returns the sum of `x` and `y`.	`x+y` or `add(x,y)`
Constant	`c` is a real valued constant.	`c`
Division	Returns the quotient of `x` and `y`. `y` must be non-zero.	`x/y` or `div(x,y)`
Input Variable	`x` is a variable in your prepared dataset.	`x`
Integer Constant	`c` is an integer constant.	`c`
Multiplication	Returns the product of `x` and `y`.	`x*y` or `mul(x,y)`
Negation	Returns the inverse of `x`.	`-x`
Subtraction	Returns the difference of `x` and `y`.	`x-y` or `sub(x,y)`

Exponential¶

Building Block	Definition	Usage
Exponential	Returns `e^x`.	`exp(x)`
Factorial	Returns the product of all positive integers from 1 to `x`.	`factorial(x)` or `x!`
Natural Logarithm	Returns the natural logarithm (base `e`) of `x`.	`log(x)`
Power	Returns `x` raised to the power of `y`. `x` and `y` can be any expression.	`x^y` or `pow(x,y)`
Square Root	Returns the square root of `x`. `x` must be positive.	`sqrt(x)`

Squashing functions¶

Squashing functions take a continuous input variable and map it to a constrained output range.

Recommended use: Depending on the shape of the particular squashing function, that function may be useful in identifying transition points in the data, and/or limiting the total impact of a particular term.

Building Block	Definition	Usage
Complementary Error Function	`1.0 - erf(x)` where `erf(x)` is the integral of the normal distribution. Returns a value between 2 and 0.	`erfc(x)`
Error Function	Integral of the normal distribution. Returns a value between -1 and +1.	`erf(x)`
Gaussian Function	Returns `exp(-x^2)`. This is a bell-shaped squashing function.	`gauss(x)`
Hyperbolic Tangent	The hyperbolic tangent of `x`. Hyperbolic tangent is a common squashing function that returns a value between -1 and +1.	`tanh(x)`
Logistic Function	Returns `1/(1+exp(-x))`. This is a common sigmoid (s-shaped) squashing function that returns a value between 0 and 1.	`logistic(x)`
Step Function	Returns 1 if `x` is positive, 0 otherwise.	`step(x)`
Sign	Returns -1 if `x` is negative, +1 if `x` is positive, and 0 if `x` is zero.	`sgn(x)`

Comparison/Boolean functions¶

Building Block	Definition	Usage
Equal To	Returns 1 if `x` is numerically equal to `y`, 0 otherwise.	`equal(x,y)` or `x=y`
Greater Than	Returns 1 if `x>y`, 0 otherwise.	`greater(x,y)` or `x>y`
Greater Than or Equal To	Returns 1 if `x>=y`, 0 otherwise.	`greater_or_equal(x,y)` or `x>=y`
If-Then-Else	Returns `y` if `x` is greater than 0, `z` otherwise. If `x` is `nan`, the function returns `z`.	`if(x,y,z)`
Less Than	Returns 1 if `x<y`, 0 otherwise.	`less(x,y)` or `x<y`
Less Than or Equal To	Returns 1 if `x<=y`, 0 otherwise.	`less_or_equal(x,y)` or `x<= y`
Logical And	Returns 1 if both `x` and `y` are greater than 0, 0 otherwise.	`and(x,y)`
Logical Exclusive Or	Returns 1 if `(x<=0 and y>0)` or `(x>0 and y<=0)`, 0 otherwise.	`xor(x,y)`
Logical Not	Returns 0 if `x` is greater than 0, 1 otherwise.	`not( x )`
Logical Or	Returns 1 if either `x` or `y` are greater than 0, 0 otherwise.	`or(x,y)`

Trigonometric functions¶

Trigonometric functions are functions of an angle; they relate the angles of a triangle to the length of its sides.

Recommended use: When modeling data from physical systems containing angles as inputs.

Building Block	Definition	Usage
Cosine	The standard trigonometric cosine function. The angle `(x)` is in radians.	`cos(x)`
Hyperbolic Cosine	The standard trigonometric hyperbolic cosine function.	`cosh(x)`
Hyperbolic Sine	The standard trigonometric hyperbolic sine function.	`sinh(x)`
Sine	The standard trigonometric sine function. The angle `(x)` is in radians.	`sin(x)`
Tangent	The standard trigonometric tangent function. The angle `(x)` is in radians.	`tan(x)`

Inverse trigonometric functions¶

Building Block	Definition	Usage
Arccosine	The standard trigonometric arccosine function.	`acos(x)`
Arcsine	The standard trigonometric arcsine function.	`asin(x)`
Arctangent	The standard trigonometric arctangent function.	`atan(x)`
Inverse Hyperbolic Cosine	The standard inverse hyperbolic cosine function.	`acosh(x)`
Inverse Hyperbolic Sine	The standard inverse hyperbolic sine function.	`asinh(x)`
Inverse Hyperbolic Tangent	The standard inverse hyperbolic tangent function.	`atanh(x)`
Two-Argument Arctangent	The standard trigonometric two-argument arctangent function.	`atan2(y,x)`

Other functions¶

Building Block	Definition	Usage
Absolute Value	Returns the positive value of `x`, without regard for its sign.	`abs(x)`
Ceiling	Returns the smallest integer not less than `x`.	`ceil(x)`
Floor	Returns the largest integer not greater than `x`.	`floor(x)`
Maximum	Returns the maximum (signed) result of `x` and `y`.	`max(x,y)`
Minimum	Returns the minimum (signed) result of `x` and `y`.	`min(x,y)`
Modulo	Returns the remainder of `x/y`.	`mod(x,y)`
Round	Returns an integer of `x` rounded to the nearest integer.	`round(x)`