ee.Number.expression

計算數字運算式。

用量傳回
ee.Number.expression(expression, vars)數字
引數類型詳細資料
expression字串要評估的數學運算式字串。除了標準算術、布林和關係運算子，運算式也支援 Number 中的任何函式、從「vars」字典擷取子元素的「.」運算子，以及數學常數 Math.PI 和 Math.E。
vars字典，預設值：null可在運算式中使用的具名值字典。

範例

程式碼編輯器 (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 設定

請參閱 Python 環境頁面，瞭解 Python API 和如何使用 geemap 進行互動式開發。

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())