Custom variables in VistaPro can be defined by combining several variables together using a formula or in other words an expression. Below describes all the operators, functions and constants available for use in your own expressions. The expression syntax is Excel like in nature so should be easy to pick up and understand.
Operators
Arithmetic
The usual arithmetic operators are supported for addition +, subtraction -, division /, multiplication *, modulo %, exponentiation ^, and negation -.
Parentheses ( , ) can be used to change the precedence of the operators.
For example: (A + B + C) / 3 computes the average of the sum of A , B and C .
All operators work in the usual way and can be used with variables, constants, or numbers.
For example: X^(-0.5) computes the inverse of the square root of X.
Modulo is defined as the remainder of a division that rounds the quotient towards minus infinity.
That is: A % B == A - FLOOR(A/B)*B.
Relational
Relational operators are also supported; the result of such an operation is either true or false (i.e., a boolean value).
Available operators are: equal to == , not equal to != , less than < , greater than > , less than or equal to <= , and greater than or equal to >= .
These can be used with the logical functions described
here.
All operators can be used with variables, constants, or numbers.
Functions
As well as operators, expressions support a standard set of functions that can be used to transform values. A complete list of all the functions available for you to use is below.
The syntax describes how to use the function in your expressions. Note: square brackets ‘[ ] ’ denote the argument is optional; while ellipsis ‘ ... ’ denote additional arguments can be specified.
Numerical / Mathematical
|
Name
|
Syntax
|
Description
|
|
ABS
|
ABS( value )
|
Returns the absolute value of a number.
|
|
ACOS
|
ACOS( value )
|
Returns the arccosine (in radians) of a number.
|
|
ACOSH
|
ACOSH( value )
|
Returns the inverse hyperbolic cosine of a number.
|
|
ASIN
|
ASIN( value )
|
Returns the arcsine (in radians) of a number.
|
|
ASINH
|
ASINH( value )
|
Returns the inverse hyperbolic sine of a number.
|
|
ATAN
|
ATAN( value )
|
Returns the arctangent (in radians) of a number.
|
|
ATAN2
|
ATAN2( x-value, y-value )
|
Returns the arctangent (in radians) of (x,y) coordinates.
|
|
ATANH
|
ATANH( value )
|
Returns the inverse hyperbolic tangent of a number.
|
|
AVG
|
AVG( value )
|
Returns the average (arithmetic mean) of the variable.
|
|
CBRT
|
CBRT( value )
|
Returns the cubic root of a number.
|
|
CEIL
|
CEIL( value )
|
Returns a number rounded up.
|
|
CLAMP
|
CLAMP( value, min, max )
|
Returns a number within the specified range.
|
|
COS
|
COS( value )
|
Returns the cosine of an angle.
|
|
COSH
|
COSH( value )
|
Returns the hyperbolic cosine of a number.
|
|
COUNT
|
COUNT( value, ... )
|
Returns the number of values which are valid, i.e. not  . |
|
DEGREES
|
DEGREES( value )
|
Converts radians into degrees.
|
|
EXP
|
EXP( value )
|
Returns mathematical constant  raised to the nth power. |
|
EXP2
|
EXP2( value )
|
Returns 2 raised to the nth power.
|
|
FLOOR
|
FLOOR( value )
|
Returns a number rounded down.
|
|
FRACT
|
FRACT( value )
|
Returns the fractional part of a number.
|
|
HYPOT
|
HYPOT( x-value, y-value )
|
Returns the hypotenuse (square root of the sum of the squares) of the coordinates.
|
|
INRANGE
|
INRANGE( value, min, max )
|
Returns true if the number is within the specified range or false if it is outside the range.
|
|
LOG
|
LOG( value, base )
|
Returns the logarithm of a number to the specified base.
|
|
LOG2
|
LOG2( value )
|
Returns the base-2 logarithm of a number.
|
|
LOG10
|
LOG10( value )
|
Returns the base-10 logarithm of a number.
|
|
LN
|
LN( value )
|
Returns the natural logarithm of a number.
|
|
MAX
|
MAX( value1, [value2] )
|
Returns the largest value(s) for the specified variable(s).
|
|
MEDIAN
|
MEDIAN( array )
|
Returns the median value in the array.
|
|
MIN
|
MIN( value1, [value2] )
|
Returns the smallest value(s) for the specified variable(s).
|
|
MOD
|
MOD( value, divisor )
|
Returns the remainder after a value is divided by a divisor.
|
|
NEG
|
NEG( value )
|
Returns true if the value is less than zero, otherwise false.
|
|
NUM
|
NUM( value )
|
Converts a true or false value to one or zero respectively.
|
|
POS
|
POS( value )
|
Returns true if the value is greater than zero, otherwise false.
|
|
POW
|
POW( value, power )
|
Returns the result of a number raised to a given power.
|
|
RADIANS
|
RADIANS( value )
|
Converts degrees to radians.
|
|
RANGE
|
RANGE( array )
|
Returns the range of values in the array.
|
|
ROTATE
|
ROTATE( array, offset )
|
Rotates elements in the array so that offset is now the start.
|
|
ROUND
|
ROUND( value )
|
Returns a number rounded to the nearest integer.
|
|
SHIFT
|
SHIFT( array, offset, [value] )
|
Shifts elements in the array so that offset is now the start while filling the gap with the specified value or . |
|
SIGN
|
SIGN( value )
|
Returns 1 if the value is greater than zero, -1 if the value is less than zero, or 0 otherwise.
|
|
SIN
|
SIN( value )
|
Returns the sine of an angle.
|
|
SINH
|
SINH( value )
|
Returns the hyperbolic sine of a number.
|
|
SQRT
|
SQRT( value )
|
Returns the square root of a number.
|
|
SUM
|
SUM( value )
|
Returns the total (summation) of a variable.
|
|
TAN
|
TAN( value )
|
Returns the tangent of an angle.
|
|
TANH
|
TANH( value )
|
Returns the hyperbolic tangent of a number.
|
|
TRUNCATE
|
TRUNCATE( value, min, max )
|
Returns the number if it is within the specified range or if it is outside the range. |
Logical
|
Name
|
Syntax
|
Description
|
|
IF
|
IF( condition, true-value, false-value )
|
Returns one value if a specified condition evaluates to true, or another value if it evaluates to false.
|
|
AND
|
AND( condition1, condition2, ... )
|
Returns true if all conditions are true, otherwise false.
|
|
OR
|
OR( condition1, condition2, ... )
|
Returns true if any conditions are true, otherwise false.
|
|
NOT
|
NOT( condition )
|
Returns the reversed logical value.
|
|
XOR
|
XOR( condition1, condition2, ... )
|
Returns true when the number of true conditions is odd and false when the number of true conditions is even.
|
|
ALL
|
ALL( value, ... )
|
Returns true if all values are true, otherwise returns false.
|
|
ANY
|
ANY( value, ... )
|
Returns true if any value is true, otherwise returns false.
|
|
NONE
|
NONE( value, ... )
|
Returns true if no values are true, otherwise returns false.
|
|
COUNTIF
|
COUNTIF( value, ... )
|
Returns the number of values which are true.
|
Constants
A list of common and model related constants is also available to use as well. A constant is just a numerical value represented with a name. These are defined below.
Model Related
|
Name
|
Description
|
Units
|
|
|
WHP
|
Weather – Heating Percentile.
|
%
|
|
|
WCP
|
Weather – Cooling Percentile.
|
%
|
|
|
WMDT
|
Weather – Maximum Dry-bulb Temperature.
|
°C , °F
|
|
|
WMWT
|
Weather – Maximum Wet-bulb Temperature.
|
°C , °F
|
|
|
WWDT
|
Weather – Winter Design Temperature.
|
°C , °F
|
|
|
WCO2
|
Weather – External CO2 concentration.
|
ppm
|
|
|
WRAD
|
Weather – Reference Air Density.
|
kg/m³ , lb/ft³
|
|
|
NR
|
Number of Rooms in Model.
|
-
|
|
|
NS
|
Number of Apache Systems in Model.
|
-
|
|
|
RA
|
Total Room Floor Area.
|
m² , ft²
|
|
|
RV
|
Room Volume.
|
m³ , ft³
|
|
|
ROA
|
Room Opaque Area.
|
m² , ft²
|
|
|
RGA
|
Room Glazed Area.
|
m² , ft²
|
|
|
RIWA
|
Room Internal Wall Area.
|
m² , ft²
|
|
|
REWA
|
Room External Wall Area.
|
m² , ft²
|
|
|
RIGA
|
Room Internal Glazed Area.
|
m² , ft²
|
|
|
REGA
|
Room External Glazed Area.
|
m² , ft²
|
|
|
RRLA
|
Room Roof Light Area.
|
m² , ft²
|
|
|
RDA
|
Room Door Area.
|
m² , ft²
|
|
|
RFA
|
Room Floor Area.
|
m² , ft²
|
|
|
RGFA
|
Room Ground Floor Area.
|
m² , ft²
|
|
|
RCA
|
Room Ceiling Area.
|
m² , ft²
|
|
|
RRA
|
Room Roof Area.
|
m² , ft²
|
|
|
RRHL
|
Lowest Relative Humidity in Room.
|
%
|
|
|
RRHH
|
Highest Relative Humidity in Room.
|
%
|
|
|
RNS
|
Number of Surfaces in Room.
|
-
|
|
|
RNO
|
Number of Openings in Room.
|
-
|
|
|
SA
|
Net Surface Area.
|
m² , ft²
|
|
|
OA
|
Gross Opening Area.
|
m² , ft²
|
|
|
SFA
|
Apache System Floor Area.
|
m² , ft²
|
|
|
SFAMV
|
Apache System Auxiliary Mechanical Ventilation Floor Area.
|
m² , ft²
|
|
|
SATD
|
Apache System Supply Air Temperature Difference.
|
°C , °F
|
|
|
SRAD
|
Apache System Reference Air Density.
|
kg/m³ , lb/ft³
|
|
Note: Model constants are only available for use with their respective data level or lower.
The values are taken directly from the apache results file so are representative of your model at the point of simulation.
Where applicable, values are in Metric or US IP units based on the current VE setting.
|
General
|
Name
|
Description
|
|
DEG
|
|
The value representing 1 degree in radians, with an approximate value of 0.01745329251.
|
|
INF
|
|
The representation of positive infinity.
|
|
LN10
|
|
The natural logarithm of 10, with an approximate value of 2.302585092994046.
|
|
LN2
|
|
The natural logarithm of 2 , with an approximate value of 0.6931471805599453.
|
|
LOG10E
|
|
The base-10 logarithm of the mathematical constant , with an approximate value of 0.4342944819032518. |
|
LOG2E
|
|
The base-2 logarithm of the mathematical constant , with an approximate value of 1.442695040888963387. |
|
NAN
|
|
Not a Number, which represents an undefined or unrepresentable value.
|
|
PI
|
|
The ratio of a circle's circumference to its diameter, with an approximate value of 3.141592653589793.
|
|
RAD
|
|
The value representing 1 radian in degrees, with an approximate value of 57.2957795131.
|
|
SQRT2
|
|
The square root of 2, with an approximate value of 1.41421356237.
|
|
SQRT3
|
|
The square root of 3, with an approximate value of 1.73205080757.
|
|
TRUE
|
|
Logical value representing true for use in conditional expressions.
|
|
FALSE
|
|
Logical value representing false for use in conditional expressions.
|
