ee.Number.expression

计算数值表达式。

用法返回
ee.Number.expression(expression, vars)数字
参数类型详细信息
expression字符串要计算的数学表达式字符串。除了标准的算术、布尔和关系运算符之外，表达式还支持 Number 中的任何函数、用于从“vars”字典中提取子元素的“.”运算符，以及数学常量 Math.PI 和 Math.E。
vars字典，默认值：null可在表达式中使用的命名值字典。

示例

代码编辑器 (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 设置

如需了解 Python API 和如何使用 geemap 进行交互式开发，请参阅 Python 环境页面。

import ee
import geemap.core as geemap

Colab (Python)

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

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

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

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

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

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

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

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

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