ee.Number.expression

  • Computes a numeric expression using a string mathematical expression and an optional dictionary of variables.

  • The expression string supports standard arithmetic, boolean, relational operators, Number functions, the '.' operator, and mathematical constants Math.PI and Math.E.

  • The vars argument allows you to provide named values that can be referenced within the expression string.

 Computes a numeric expression.

UsageReturns
ee.Number.expression(expression, vars)Number
ArgumentTypeDetails
expressionStringA mathematical expression string to be evaluated. In addition to the standard arithmetic, boolean and relational operators, expressions also support any function in Number, the '.' operator to extract child elements from the 'vars' dictionary, and mathematical constants Math.PI and Math.E.
varsDictionary, default: nullA dictionary of named values that can be used in the expression.

Examples

Code Editor (JavaScript)

// A dictionary of variables to use in expression.
var variables = {x: 5, y: 10};

// Arithmetic operators.
print('x + y',
      ee.Number.expression('x + y', variables));
print('x - y',
      ee.Number.expression('x - y', variables));
print('x * y',
      ee.Number.expression('x * y', variables));
print('x / y',
      ee.Number.expression('x / y', variables));
print('x ** y',
      ee.Number.expression('x ** y', variables));
print('x % y',
      ee.Number.expression('x % y', variables));

// Logical operators.
print('x || y',
      ee.Number.expression('x || y', variables));
print('x && y',
      ee.Number.expression('x && y', variables));
print('!(x)',
      ee.Number.expression('!(x)', variables));

// Relational operators.
print('x > y',
      ee.Number.expression('x > y', variables));
print('x >= y',
      ee.Number.expression('x >= y', variables));
print('x < y',
      ee.Number.expression('x < y', variables));
print('x <= y',
      ee.Number.expression('x <= y', variables));
print('x == y',
      ee.Number.expression('x == y', variables));
print('x != y',
      ee.Number.expression('x != y', variables));

// Conditional (ternary) operator.
print('(x < y) ? 100 : 1000)',
      ee.Number.expression('(x < y) ? 100 : 1000', variables));

// Constants in the expression.
print('100 * (x + y)',
      ee.Number.expression('100 * (x + y)', variables));

// JavaScript Math constants.
print('Math.PI',
      ee.Number.expression('Math.PI', null));
print('Math.E',
      ee.Number.expression('Math.E', null));

// Dot notation to call on child elements.
print('Use dot notation to call on child elements',
      ee.Number.expression('vals.x * vals.y', {vals: variables}));

// ee.Number functions.
print('Use ee.Number add: add(x, y)',
      ee.Number.expression('add(x, y)', variables));
print('Use ee.Number add and subtract: subtract(add(x, y), 5)',
      ee.Number.expression('subtract(add(x, y), 5)', variables));

Python setup

See the Python Environment page for information on the Python API and using geemap for interactive development.

import ee
import geemap.core as geemap

Colab (Python)

# A dictionary of variables to use in expression.
variables = {'x': 5, 'y': 10}

# Arithmetic operators.
print('x + y:',
      ee.Number.expression('x + y', variables).getInfo())
print('x - y:',
      ee.Number.expression('x - y', variables).getInfo())
print('x * y:',
      ee.Number.expression('x * y', variables).getInfo())
print('x / y:',
      ee.Number.expression('x / y', variables).getInfo())
print('x ** y:',
      ee.Number.expression('x ** y', variables).getInfo())
print('x % y:',
      ee.Number.expression('x % y', variables).getInfo())

# Logical operators.
print('x || y:',
      ee.Number.expression('x || y', variables).getInfo())
print('x && y:',
      ee.Number.expression('x && y', variables).getInfo())
print('!(x):',
      ee.Number.expression('!(x)', variables).getInfo())

# Relational operators.
print('x > y:',
      ee.Number.expression('x > y', variables).getInfo())
print('x >= y:',
      ee.Number.expression('x >= y', variables).getInfo())
print('x < y:',
      ee.Number.expression('x < y', variables).getInfo())
print('x <= y:',
      ee.Number.expression('x <= y', variables).getInfo())
print('x == y:',
      ee.Number.expression('x == y', variables).getInfo())
print('x != y:',
      ee.Number.expression('x != y', variables).getInfo())

# Conditional JavaScript (ternary) operator.
print('(x < y) ? 100 : 1000):',
      ee.Number.expression('(x < y) ? 100 : 1000', variables).getInfo())

# Constants in the expression.
print('100 * (x + y):',
      ee.Number.expression('100 * (x + y)', variables).getInfo())

# JavaScript Math constants.
print('Math.PI:',
      ee.Number.expression('Math.PI', None).getInfo())
print('Math.E:',
      ee.Number.expression('Math.E', None).getInfo())

# Dot notation to call on child elements.
print('Use dot notation to call on child elements:',
      ee.Number.expression('vals.x * vals.y', {'vals': variables}).getInfo())

# ee.Number functions.
print('Use ee.Number add. add(x, y):',
      ee.Number.expression('add(x, y)', variables).getInfo())
print('Use ee.Number add and subtract. subtract(add(x, y), 5):',
      ee.Number.expression('subtract(add(x, y), 5)', variables).getInfo())