【GEE笔记11】数值Number（常见指令方法4）

GEE有很多类型的数据

• String
• Number
• Array
• List
• Dictionary
• Geometry
• Feature
• FeatureCollection
• Image
• ImageCollection
• 各种卫星数据

本文主要介绍ee.Number的常见指令方法内容，完整指令方法见GEE ee.Number

ee.Number有以下常见指令方法内容

1. 显示print(number)
2. 创建ee.Number()
3. 比较ee.Number.eq() 、ee.Number.neq()、ee.Number.lt()、ee.Number.lte()、ee.Number.gt()、ee.Number.gte()
4. 缩放ee.Number.unitScale
5. 取整
   • 绝对值ee.Number.abs
   • 四舍五入ee.Number.round
   • 向下取整ee.Number.ceil
   • 向上取整ee.Number.floor
6. 底数e的幂ee.Number.exp
7. 链式调用ee.Number.aside
8. 函数运算
   • 开方ee.Number.sqrt
   • 三次根ee.Number.cbrt
   • 幂ee.Number.pow
   • logee.Number.log
   • log10（lg）ee.Number.log10
   • 最大值ee.Number.max
   • 最小值ee.Number.min
   • 三角形斜边ee.Number.hypot
   • 第一个数值ee.Number.first
   • 第一个非零数值ee.Number.firstNonZero
9. 逻辑运算

• ee.Number.and
• ee.Number.or
• ee.Number.not

10. 数学运算
    • 加ee.Number.add
    • 减ee.Number.subtract
    • 乘ee.Number.multiply
    • 除ee.Number.divide
    • 余数ee.Number.mod
11. 三角函数（正、反、双曲）
    • sinee.Number.sin
    • cosee.Number.cos
    • tanee.Number.tan
    • asinee.Number.asin
    • acosee.Number.acos
    • atanee.Number.atan
    • sinhee.Number.sinh
    • coshee.Number.cosh
    • tanhee.Number.tanh
12. sign函数ee.Number.signum
13. 按位运算
    • 按位与ee.Number.bitwiseAnd
    • 按位非ee.Number.bitwiseNot
    • 按位或ee.Number.bitwiseOr
    • 按位异或ee.Number.bitwiseXor
14. 移位运算
    • 左移ee.Number.leftShift
    • 右移ee.Number.rightShift
15. Gamma函数

• ee.Number.trigamma
• ee.Number.gamma
• ee.Number.gammainc
• ee.Number.digamma

16. 计算二维向量角度ee.Number.atan2
17. 限制数值范围ee.Number.clamp
18. 字符转数值ee.Number.parse
19. 数值转字符ee.Number.format
20. 格式转换
    • int(toInt)ee.Number.int / ee.Number.toInt
    • int8/16/32/64（toInt8/16/32/64）
    • long / toLongee.Number.long / ee.Number.toLong
    • short / toShortee.Number.short / ee.Number.toShort
    • byte / toByteee.Number.byte / ee.Number.toByte
    • double / toDoubleee.Number.double / ee.Number.toDouble
    • float / toFloatee.Number.float / ee.Number.toFloat
    • uint8/16/32（toUint8/16/32）

前置章节请阅读
【GEE笔记8】数值Number（常见指令方法1）
【GEE笔记9】数值Number（常见指令方法2）
【GEE笔记10】数值Number（常见指令方法3）

16. 计算二维向量角度ee.Number.atan2

输入一个点的二维坐标，计算这个点和坐标轴连线形成的角度（弧度制）

用法

Number.atan2(right)
1

案例

// Left input is x and right input is y, representing point (x,y).
print('Atan2 of point (0,0)', ee.Number(0).atan2(0));  // 0
print('Atan2 of point (1,0)', ee.Number(1).atan2(0));  // 0
print('Atan2 of point (0,1)', ee.Number(0).atan2(1));  // 1.570796326 (π/2)
print('Atan2 of point (-1,0)', ee.Number(-1).atan2(0));  // 3.141592653 (π)
print('Atan2 of point (0,-1)', ee.Number(0).atan2(-1));  // -1.570796326 (-π/2)
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17. 限制数值范围ee.Number.clamp

用法

Number.clamp(min, max)
1

案例

// Numbers within range are unaffected.
print('100 clamped to range [0,255]', ee.Number(100).clamp(0, 255));  // 100

// Numbers greater than max in range are set to max.
print('259 clamped to range [0,255]', ee.Number(259).clamp(0, 255));  // 255

// Numbers less than min in range are set to min.
print('-259 clamped to range [0,255]', ee.Number(-259).clamp(0, 255));  // 0
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18. 字符转数值ee.Number.parse

用法

ee.Number.parse(input, radix)
1

案例

print('Client-side string converted to ee.Number',
      ee.Number.parse('10'));  // 10

print('ee.String converted to ee.Number',
      ee.Number.parse(ee.String('100')));  // 100

print('Ambiguous string object converted to ee.Number',
      ee.Number.parse(ee.Feature(null, {id: '1000'}).get('id')));  // 1000

print('Ambiguous number object converted to ee.Number',
      ee.Number.parse(ee.Feature(null, {id: 1000}).get('id')));  // 1000

print('Leading zeros are removed',
      ee.Number.parse('0001'));  // 1
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19. 数值转字符ee.Number.format

用法

Number.format(pattern)
1

pattern
一个 printf 样式的格式字符串。
例如，“%.2f”生成格式为“3.14”的数字，“%05d”生成格式为“00042”的数字。

格式字符串必须满足以下条件： 1. 零个或多个前缀字符。 2. 正好是一个 ‘%’。 3. 集合 [#-+ 0,(.\d] 中的零个或多个修饰符。 4. 集合 [sdoxXeEfgGaA] 中的恰好一个转换字符。 5. 零个或多个后缀字符。
有关格式字符串的更多信息，请参阅https://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html

案例

print('Zero-fill to length of 3',
      ee.Number(1).format('%03d'));  // 001

print('Include 1 decimal place in 1.2347',
      ee.Number(1.23476).format('%.1f'));  // 1.2

print('Include 3 decimal places in 1.2347',
      ee.Number(1.23476).format('%.3f'));  // 1.235 (rounds up)

print('Scientific notation with 3 decimal places shown',
      ee.Number(123476).format('%.3e'));  // 1.235e+05 (rounds up)

print('Integer with 2 decimal places of precision',
      ee.Number(123476).format('%.2f'));  // 123476.00
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20. 格式转换

int：singed integer（有符号整数）
uint：unsigned integer（无符号整数）

• int(toInt)ee.Number.int / ee.Number.toInt
  将输入值转换为带符号的 32 位整数。
  代码区域只展示int的用法，如果用toInt，就是把int改成toInt。

用法

Number.int()
1

案例

// Cast a number to signed 32-bit integer: [-2147483648, 2147483647].
var number = ee.Number(100);
print('Number:', number);

var intNumber = number.int();
print('Number cast to int:', intNumber);


/**
 * Casting numbers to int that are outside of its range and precision can
 * modify the resulting value, note the behavior of the following scenarios.
 */

// A floating point number cast to int loses decimal precision.
var float = ee.Number(1.7);
print('Floating point value:', float);

var floatToInt = float.int();
print('Floating point value cast to int:', floatToInt);

// A number greater than int range max cast to int becomes int range max.
var INT_MAX = 2147483647;
var outOfRangeHi = ee.Number(INT_MAX + 12345);
print('Greater than int max:', outOfRangeHi);

var outOfRangeHiToInt = outOfRangeHi.int();
print('Greater than int max cast to int becomes int max:', outOfRangeHiToInt);

// A number greater than int range min cast to int becomes int range min.
var INT_MIN = -2147483648;
var outOfRangeLo = ee.Number(INT_MIN - 12345);
print('Less than int min:', outOfRangeLo);

var outOfRangeLoToInt = outOfRangeLo.int();
print('Less than int min cast to int becomes int min:', outOfRangeLoToInt);
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• int8/16/32/64（toInt8/16/32/64）

用法

Number.int8()
1

案例

// Cast a number to signed 8-bit integer: [-128, 127].
var number = ee.Number(100);
print('Number:', number);

var int8Number = number.int8();
print('Number cast to int8:', int8Number);


/**
 * Casting numbers to int8 that are outside of its range and precision can
 * modify the resulting value, note the behavior of the following scenarios.
 */

// A floating point number cast to int8 loses decimal precision.
var float = ee.Number(1.7);
print('Floating point value:', float);

var floatToInt8 = float.int8();
print('Floating point value cast to int8:', floatToInt8);

// A number greater than int8 range max cast to int8 becomes int8 range max.
var INT8_MAX = 127;
var outOfRangeHi = ee.Number(INT8_MAX + 12345);
print('Greater than int8 max:', outOfRangeHi);

var outOfRangeHiToInt8 = outOfRangeHi.int8();
print('Greater than int8 max cast to int8 becomes int8 max:', outOfRangeHiToInt8);

// A number greater than int8 range min cast to int8 becomes int8 range min.
var INT8_MIN = -128;
var outOfRangeLo = ee.Number(INT8_MIN - 12345);
print('Less than int8 min:', outOfRangeLo);

var outOfRangeLoToInt8 = outOfRangeLo.int8();
print('Less than int8 min cast to int8 becomes int8 min:', outOfRangeLoToInt8);
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• long / toLongee.Number.long / ee.Number.toLong
  将输入值转换为有符号的 64 位整数。

用法

Number.long()
1

案例

// Declare an ee.Number.
var number = ee.Number(100);
print('ee.Number:', number);

// Cast a number to signed 64-bit integer.
var longNumber = number.long();
print('ee.Number cast to long:', longNumber);


/**
* Casting numbers to long that are outside of its range and precision can
* modify the resulting value, note the behavior of the following scenarios.
*/

// A floating point number cast to long loses decimal precision.
var float = ee.Number(1.7);
print('Floating point value:', float);

var floatToLong = float.long();
print('Floating point value cast to long:', floatToLong);
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• short / toShortee.Number.short / ee.Number.toShort
  将输入值转换为有符号的 16 位整数

用法

Number.short()
1

案例

// Cast a number to signed 16-bit integer: [-32768, 32767].
var number = ee.Number(100);
print('Number:', number);

var shortNumber = number.short();
print('Number cast to short:', shortNumber);


/**
 * Casting numbers to short that are outside of its range and precision can
 * modify the resulting value, note the behavior of the following scenarios.
 */

// A floating point number cast to short loses decimal precision.
var float = ee.Number(1.7);
print('Floating point value:', float);

var floatToShort = float.short();
print('Floating point value cast to short:', floatToShort);

// A number greater than short range max cast to short becomes short range max.
var SHORT_MAX = 32767;
var outOfRangeHi = ee.Number(SHORT_MAX + 12345);
print('Greater than short max:', outOfRangeHi);

var outOfRangeHiToShort = outOfRangeHi.short();
print('Greater than short max cast to short becomes short max:', outOfRangeHiToShort);

// A number greater than short range min cast to short becomes short range min.
var SHORT_MIN = -32768;
var outOfRangeLo = ee.Number(SHORT_MIN - 12345);
print('Less than short min:', outOfRangeLo);

var outOfRangeLoToShort = outOfRangeLo.short();
print('Less than short min cast to short becomes short min:', outOfRangeLoToShort);
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• byte / toByteee.Number.byte / ee.Number.toByte
  将输入值转换为无符号 8 位整数。

用法

Number.byte()
1

案例

// Cast a number to unsigned 8-bit integer: [0, 255].
var number = ee.Number(100);
print('Number:', number);

var byteNumber = number.byte();
print('Number cast to byte:', byteNumber);


/**
 * Casting numbers to byte that are outside of its range and precision can
 * modify the resulting value, note the behavior of the following scenarios.
 */

// A floating point number cast to byte loses decimal precision.
var float = ee.Number(1.7);
print('Floating point value:', float);

var floatToByte = float.byte();
print('Floating point value cast to byte:', floatToByte);

// A number greater than byte range max cast to byte becomes byte range max.
var BYTE_MAX = 255;
var outOfRangeHi = ee.Number(BYTE_MAX + 12345);
print('Greater than byte max:', outOfRangeHi);

var outOfRangeHiToByte = outOfRangeHi.byte();
print('Greater than byte max cast to byte becomes byte max:', outOfRangeHiToByte);

// A number greater than byte range min cast to byte becomes byte range min.
var BYTE_MIN = 0;
var outOfRangeLo = ee.Number(BYTE_MIN - 12345);
print('Less than byte min:', outOfRangeLo);

var outOfRangeLoToByte = outOfRangeLo.byte();
print('Less than byte min cast to byte becomes byte min:', outOfRangeLoToByte);
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• double / toDoubleee.Number.double / ee.Number.toDouble
  将输入值转换为 64 位浮点数。

用法

Number.double()
1

案例

// Declare an ee.Number.
var number = ee.Number(100);
print('ee.Number:', number);

// Cast a number to signed 64-bit floating point.
var doubleNumber = number.double();
print('ee.Number cast to double:', doubleNumber);
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• float / toFloatee.Number.float / ee.Number.toFloat
  将输入值转换为 32 位浮点数。

用法

Number.float()
1

案例

// Declare an ee.Number.
var number = ee.Number(100);
print('ee.Number:', number);

// Cast a number to signed 32-bit floating point.
var floatNumber = number.float();
print('ee.Number cast to float:', floatNumber);
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• uint8/16/32（toUint8/16/32）
  将输入值转换为无符号 8 位整数。

用法

Number.uint8()
1

案例

// Cast a number to unsigned 8-bit integer: [0, 255].
var number = ee.Number(100);
print('Number:', number);

var uint8Number = number.uint8();
print('Number cast to uint8:', uint8Number);


/**
 * Casting numbers to uint8 that are outside of its range and precision can
 * modify the resulting value, note the behavior of the following scenarios.
 */

// A floating point number cast to uint8 loses decimal precision.
var float = ee.Number(1.7);
print('Floating point value:', float);

var floatToUint8 = float.uint8();
print('Floating point value cast to uint8:', floatToUint8);

// A number greater than uint8 range max cast to uint8 becomes uint8 range max.
var UINT8_MAX = 255;
var outOfRangeHi = ee.Number(UINT8_MAX + 12345);
print('Greater than uint8 max:', outOfRangeHi);

var outOfRangeHiToUint8 = outOfRangeHi.uint8();
print('Greater than uint8 max cast to uint8 becomes uint8 max:', outOfRangeHiToUint8);

// A number greater than uint8 range min cast to uint8 becomes uint8 range min.
var UINT8_MIN = 0;
var outOfRangeLo = ee.Number(UINT8_MIN - 12345);
print('Less than uint8 min:', outOfRangeLo);

var outOfRangeLoToUint8 = outOfRangeLo.uint8();
print('Less than uint8 min cast to uint8 becomes uint8 min:', outOfRangeLoToUint8);
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