Expression Editor

The expression editor is the text field behind calculated values in dashboards, diagrams and virtual variables. An expression references Device Variables, combines them with arithmetic and logic, and is re-evaluated each time one of those Variables reports a new value. This page is the syntax reference.

Workflow Stage: Visualize

Overview

An expression is a single line of text such as {{temp1}} + {{temp2}}. It can reference any Variable the component has access to, apply the operators and functions listed below, and return a number, a string or a boolean. The result is recomputed whenever a referenced Variable changes, so a widget or diagram element bound to an expression stays current without any further configuration.

Basic Usage

Expressions appear in three places. Dashboard widgets use them for calculated values, conditional formatting and dynamic text. Diagram elements use them for status indicators, calculated displays and conditional visibility. Virtual Variables use them to define a computed data point from existing Variables.

Syntax

An expression combines Variable references, literals, operators and function calls:

{{variable1}} + {{variable2}} * 2

Variables

Reference a Device Variable by wrapping its identifier in double curly braces:

Variable Syntax

{{deviceId.variableId}}

Variable Types

Number: Numeric values that support mathematical operations
String: Text values that can be concatenated and compared
Boolean: True/false values for logical operations

Operators

Arithmetic Operators

Operator	Description	Example
`+`	Addition	`{{temp1}} + {{temp2}}`
`-`	Subtraction	`{{temp1}} - {{temp2}}`
`*`	Multiplication	`{{power}} * 1.5`
`/`	Division	`{{total}} / {{count}}`
`%`	Remainder	`{{value}} % 10`
`^`	Exponentiation	`{{base}} ^ 2`

Comparison Operators

Operator	Description	Example
`==`	Equal to	`{{status}} == "online"`
`!=`	Not equal to	`{{status}} != "offline"`
`<`	Less than	`{{temp}} < 75`
`<=`	Less than or equal	`{{temp}} <= 75`
`>`	Greater than	`{{temp}} > 85`
`>=`	Greater than or equal	`{{temp}} >= 85`

Logical Operators

Operator	Description	Example
`and`	Logical AND	`{{temp}} > 70 and {{temp}} < 90`
`or`	Logical OR	`{{status}} == "alarm" or {{status}} == "warning"`
`not`	Logical NOT	`not {{maintenance}}`

Unary Operators

Operator	Description	Example
`-`	Negation	`-{{value}}`
`+`	Positive	`+{{value}}`
`abs`	Absolute value	`abs {{difference}}`
`sqrt`	Square root	`sqrt {{area}}`
`ceil`	Round up	`ceil {{value}}`
`floor`	Round down	`floor {{value}}`

Mathematical Functions

Basic Math Functions

min(a, b, ...) - Returns the smallest value
max(a, b, ...) - Returns the largest value
pow(base, exponent) - Raises base to the power of exponent
random() - Returns a random number between 0 and 1

Trigonometric Functions

sin(x) - Sine function
cos(x) - Cosine function
tan(x) - Tangent function
asin(x) - Arcsine function
acos(x) - Arccosine function
atan(x) - Arctangent function
atan2(y, x) - Two-argument arctangent

Logarithmic Functions

ln(x) - Natural logarithm
log(x) - Natural logarithm (alias for ln)
log10(x) - Base-10 logarithm

Utility Functions

round(x) - Rounds to nearest integer
sign(x) - Returns -1, 0, or 1 based on sign
hypot(a, b, ...) - Euclidean distance (hypotenuse)

Logical Functions

Conditional Function

The if function provides conditional logic:

if(condition, value_if_true, value_if_false)

Examples:

if({{temperature}} > 80, "Hot", "Normal")
if({{status}} == "online", 1, 0)
if({{power}} > 100, {{power}} * 0.9, {{power}})

Ternary Operator

You can also use the ternary conditional operator:

{{temperature}} > 80 ? "Hot" : "Normal"

Array Functions

These functions operate on array values:

Array Operations

map(array, expression) - Transform each element
filter(array, condition) - Filter elements by condition
fold(array, initial, expression) - Reduce array to single value
indexOf(array, value) - Find index of value
join(array, separator) - Join array elements into string
length(array) - Get array length

Constants

The following constants are available in every expression:

Mathematical Constants

PI - π (3.14159...)
E - Euler's number (2.71828...)

Boolean Constants

true - Boolean true value
false - Boolean false value

Best Practices

Performance

Keep expressions simple when possible
Avoid complex nested calculations in frequently updated components
Use parentheses to clarify operator precedence

Readability

Use descriptive variable names
Break complex expressions into multiple simpler ones
Add comments in dashboard configurations to explain complex logic

Error Handling

Test expressions with edge cases (null values, zero division)
Use conditional checks before mathematical operations
Provide fallback values for unreliable data sources

Examples

Temperature Monitoring

// Temperature status indicator
if({{sensor.temperature}} > 85, "Critical", 
   if({{sensor.temperature}} > 75, "Warning", "Normal"))

// Temperature in Fahrenheit from Celsius
{{sensor.tempC}} * 9/5 + 32

Power Calculations

// Power efficiency percentage
({{generator.actualPower}} / {{generator.ratedPower}}) * 100

// Total power consumption
{{load1.power}} + {{load2.power}} + {{load3.power}}

// Power factor calculation
{{realPower}} / sqrt({{realPower}}^2 + {{reactivePower}}^2)

Status Logic

// System health indicator
if({{device.online}} and {{device.errors}} == 0, "Healthy", 
   if({{device.online}}, "Degraded", "Offline"))

// Alarm condition
{{temperature}} > 90 or {{pressure}} > 150 or not {{safety.ok}}

Time-based Calculations

// Runtime hours from milliseconds
{{runtime.totalMs}} / (1000 * 60 * 60)

// Efficiency over time
{{totalOutput}} / {{totalInput}} * 100

Complex Conditional Logic

// Multi-tier alarm severity
if({{criticalAlarms}} > 0, "Critical",
   if({{majorAlarms}} > 0, "Major",
      if({{minorAlarms}} > 0, "Minor", "Normal")))

// Load balancing calculation
if({{load}} > {{capacity}} * 0.8, 
   "Reduce Load", 
   if({{load}} < {{capacity}} * 0.3, "Increase Load", "Optimal"))