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VistaPro User Guide
Custom Variable Expressions
IES Virtual Environment
Copyright © 2015 Integrated Environmental Solutions Limited. All rights reserved.
No part of the manual is to be copied or reproduced in any form without the express agreement of
Integrated Environmental Solutions Limited.
Contents
1 Expressions.................................................................................................................................2
1.1 Operators ............................................................................................................................2
1.1.1
1.1.2
Arithmetic .................................................................................................................................................... 2
Relational ..................................................................................................................................................... 2
1.2 Functions .............................................................................................................................3
1.2.1
1.2.2
Numerical / Mathematical ........................................................................................................................... 3
Logical .......................................................................................................................................................... 4
1.3 Constants ............................................................................................................................4
1.3.1
1.3.2
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Model Related ............................................................................................................................................. 4
General ........................................................................................................................................................ 5
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1
Expressions
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.
1.1 Operators
1.1.1 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.
1.1.2 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.
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1.2 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.
1.2.1 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.
ASIN
ASIN( value )
Returns the arcsine (in radians) 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.
AVG
AVG( value )
Returns the average (arithmetic mean) of the variable.
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.
DEGREES
DEGREES( value )
Converts radians into degrees.
EXP
EXP( value )
Returns mathematical constant 𝑒 raised to the nth power.
FLOOR
FLOOR( value )
Returns a number rounded down.
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.
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).
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.
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SIGN
SIGN( value )
Returns 1 if the value is greater than zero, -1 if the value is less
than zero, 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 𝑁𝑎𝑁 if it
is outside the range.
1.2.2 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.
1.3 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.
1.3.1 Model Related
Name
Description
RA1
Room Floor Area.
RV1
Room Volume.
SA2
Net Surface Area.
OA3
Gross Opening Area.
SFA4
Apache System Floor Area.
SFAMV4 Apache System Auxiliary Mechanical Ventilation Floor Area.
SATD4
1
3
Apache System Supply Air Temperature Difference.
- only available for use with Room, Surface and Opening level variables
- only available for use with Opening level variables
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- only available for use with Surface and Opening level variables
- only available for use with Apache System level variables
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1.3.2 General
Name
Description
DEG
𝜋⁄
180
INF
∞
The value representing 1 degree in radians, with an approximate value of 0.01745329251.
The representation of positive infinity.
LN10
ln 10
The natural logarithm of 10, with an approximate value of 2.302585092994046.
LN2
ln 2
The natural logarithm of 2, with an approximate value of 0.6931471805599453.
LOG10E
log10 𝑒
The base-10 logarithm of the mathematical constant 𝑒, with an approximate value of
0.4342944819032518.
LOG2E
log 2 𝑒
The base-2 logarithm of the mathematical constant 𝑒, with an approximate value of
1.442695040888963387.
NAN
𝑁𝑎𝑁
Not a Number, which represents an undefined or unrepresentable value.
PI
RAD
𝜋
180⁄
𝜋
The ratio of a circle's circumference to its diameter, with an approximate value of
3.141592653589793.
The value representing 1 radian in degrees, with an approximate value of 57.2957795131.
SQRT2
√2
The square root of 2, with an approximate value of 1.41421356237.
SQRT3
√3
The square root of 3, with an approximate value of 1.73205080757.
TRUE
𝑡𝑟𝑢𝑒
Logical value representing true for use in conditional expressions.
FALSE
𝑓𝑎𝑙𝑠𝑒
Logical value representing false for use in conditional expressions.
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