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EntityInstance[entity,qualval]

表示限定符 qual 的值为 val 的实体.

EntityInstance[entity,{qual1val1,qual2val2,…}]

表示限定符 quali 的值为 vali 的实体.

EntityInstance[entity,quantity]

表示由 quantity 限定的实体.

更多信息
Details and Options Details and Options
范例  
基本范例  
范围  
属性限定符  
日期  
纯函数参数  
物理量变量值  
量  
Entity Store  
属性和关系  
巧妙范例  
参见
相关指南
相关链接
历史
按以下格式引用：

EntityInstance

EntityInstance[entity,qualval]

表示限定符 qual 的值为 val 的实体.

EntityInstance[entity,{qual1val1,qual2val2,…}]

表示限定符 quali 的值为 vali 的实体.

EntityInstance[entity,quantity]

表示由 quantity 限定的实体.

更多信息

  • Entity 表达式可使用 界面来创建.
  • 限定符 qual 可以是 entity 的实体属性 EntityProperty、实体变量 QuantityVariable 或函数 Function 参数的属性限定符.
  • 如果 entity[property] 返回 Function[params,body]，其中一个参数等于 qual，则将相关值替换为 body，并从 params 中删除 qual. 如果没有参数，则删除 Function 的封装.

范例

打开所有单元 关闭所有单元

基本范例  (4)

表示1950年的爱尔兰：

Wolfram Language code: EntityInstance[Entity["Country", "Ireland"], "Date" -> 1950]

返回那一时期的人口数量：

Wolfram Language code: EntityValue[%, "Population"]

指定作为纯函数返回的属性的值：

Wolfram Language code: Entity["Solid", "HalfTorus"]["SurfaceArea"]
Wolfram Language code: EntityValue[ EntityInstance[Entity["Solid", "HalfTorus"], { -> 1,  -> 2}], "SurfaceArea" ]

为多个属性指定同一值：

Wolfram Language code: EntityValue[ EntityInstance[Entity["Solid", "Ball"],  -> 1], {"SurfaceArea", "Volume"} ]

指定一个含有数量变量的属性的值：

Wolfram Language code: EntityValue[ EntityInstance[Entity["PhysicalSystem", "HarmonicOscillator1D"], ω -> Quantity[1, "Radians"/"Seconds"]], {"Lagrangian", "EquationsOfMotion"}, "PropertyAssociation" ]

指定物质的质量：

Wolfram Language code: EntityValue[EntityInstance[Entity["Chemical", "MolecularOxygen"], Quantity[1, "Kilograms"]], "AbsoluteVolume"]

范围  (8)

属性限定符  (2)

使用属性内部的限定符来指定1980年的一个属性：

Wolfram Language code: EntityValue[Entity["Country", "Spain"], {EntityProperty["Country", "Population", "Date" -> 1980], EntityProperty["Country", "PopulationGrowth", "Date" -> 1980]}]

这等价于使用一个带有未限定属性的实体实例：

Wolfram Language code: EntityValue[EntityInstance[Entity["Country", "Spain"], "Date" -> 1980], {EntityProperty["Country", "Population"], EntityProperty["Country", "PopulationGrowth"]}]

忽略不适用的限定符：

Wolfram Language code: EntityValue[EntityInstance[Entity["Country", "Spain"], "Date" -> 1980], "Name"]

日期  (1)

在只有一个限定符的情况下，一个实体实例中的日期限定符可被指定为一条规则：

Wolfram Language code: EntityValue[EntityInstance[Entity["Country", "Ireland"], "Date" -> 1950], "Population"]

指定为一个规则列表：

Wolfram Language code: EntityValue[EntityInstance[Entity["Country", "Ireland"], {"Date" -> 1950}], "Population"]

或指定为日期对象 DateObject：

Wolfram Language code: EntityValue[EntityInstance[Entity["Country", "Ireland"], DateObject[{1950}]], "Population"]

纯函数参数  (1)

获取固体属性中出现的变量：

Wolfram Language code: Entity["Solid", "HalfTorus"][EntityProperty["Solid", "Variables"]]

该属性为这些变量的纯函数：

Wolfram Language code: Entity["Solid", "HalfTorus"][{EntityProperty["Solid", "Centroid"], EntityProperty["Solid", "SurfaceArea"], EntityProperty["Solid", "Inequalities"]}]

指定 c 来获取剩余变量的函数：

Wolfram Language code: EntityValue[EntityInstance[Entity["Solid", "HalfTorus"], { -> 10}], {EntityProperty["Solid", "Centroid"], EntityProperty["Solid", "SurfaceArea"], EntityProperty["Solid", "Inequalities"]}]

指定所有变量：

Wolfram Language code: EntityValue[EntityInstance[Entity["Solid", "HalfTorus"], { -> 10,  -> 2}], {EntityProperty["Solid", "Centroid"], EntityProperty["Solid", "SurfaceArea"], EntityProperty["Solid", "Inequalities"]}]

物理量变量值  (1)

获取决定一个谐振子（harmonic oscillator）的变量：

Wolfram Language code: Entity["PhysicalSystem", "HarmonicOscillator1D"][EntityProperty["PhysicalSystem", "SystemVariables"]]

指定物理量变量：

Wolfram Language code: EntityValue[EntityInstance[Entity["PhysicalSystem", "HarmonicOscillator1D"], {QuantityVariable["m", "Mass"] -> 1, QuantityVariable["ω", "AngularFrequency"] -> 1}], "EquationsOfMotionSolution"]

量  (2)

指定 1 摩尔水：

Wolfram Language code: EntityInstance[Entity["Chemical", "Water"], Quantity[1, "Moles"]]

获取其质量：

Wolfram Language code: EntityValue[%, "AbsoluteMass"]

使用摩尔质量计算其质量：

Wolfram Language code: Entity["Chemical", "Water"][EntityProperty["Chemical", "MolarMass"]]Quantity[1, "Moles"]

结果相同：

Wolfram Language code: % == %%

指定 50 克牛角面包：

Wolfram Language code: EntityInstance[ Entity["Food", { "FoodType" -> Entity["FoodType", "Croissant"], "RelativeWaterContent" -> Quantity[Interval[{0, 0.5}], "Grams" / "Grams"] }], Quantity[50, "Grams"] ]

获取维生素 A 的含量：

Wolfram Language code: %["AbsoluteVitaminAContent"]

Entity Store  (1)

注册 "shape" 实体：

Wolfram Language code: EntityRegister[EntityStore["shape" -> <| "Entities" -> <| "rectangle" -> <|"variables" -> {, }, "area" -> Function[{, },  * ]|>, "disk" -> <|"variables" -> {}, "area" -> Function[, π *  ^ 2]|> |> |>]]

表示一个半径为 2 米的圆盘：

Wolfram Language code: EntityInstance[Entity["shape", "disk"],  -> Quantity[2, "Meters"]]

获取其面积：

Wolfram Language code: %["area"]

一个边已被指定的矩形：

Wolfram Language code: EntityInstance[Entity["shape", "rectangle"],  -> Quantity[9, "Centimeters"]]

给出作为另一个边的 Function 的面积：

Wolfram Language code: %["area"]

取消 "shape" 实体：

Wolfram Language code: EntityUnregister["shape"]

属性和关系  (1)

静默忽略包含未知或不能使用实例的表达式：

Wolfram Language code: EntityValue[ Entity["Solid", "HalfTorus"], "SurfaceArea" ]
Wolfram Language code: EntityValue[ EntityInstance[Entity["Solid", "HalfTorus"], {"blah" -> 2}], "SurfaceArea" ]

包含多个实例的表达式只应用于可应用的实例：

Wolfram Language code: EntityValue[ EntityInstance[Entity["Solid", "HalfTorus"], {"blah" -> 2,  -> 1}], "SurfaceArea" ]

巧妙范例  (1)

获取一个双摆的运动方程：

Wolfram Language code: eqn = EntityValue[ EntityInstance[Entity["PhysicalSystem", "DoublePendulum"], {Subscript[l, 1] -> 1, Subscript[m, 1] -> 1, Subscript[l, 2] -> 1, Subscript[m, 2] -> 1, g -> 9.81}], "EquationsOfMotion" ]

选择初始情况：

Wolfram Language code: theta10 = 0.7; theta20 = 0;

解方程：

Wolfram Language code: {theta1sol, theta2sol} = NDSolveValue[ Join[ eqn /. {Subscript[θ, 1] -> theta1, Subscript[θ, 2] -> theta2}, { theta1[0] == theta10, theta1'[0] == 0, theta2[0] == theta20, theta2'[0] == 0 } ], {theta1, theta2}, {t, 0, 10} ]

绘制两臂时间发展的图：

Wolfram Language code: Plot[{theta1sol[t], theta2sol[t]}, {t, 0, 10}]

将双摆动画化：

Wolfram Language code: Animate[ Graphics[{ Disk[{0, 0}, 0.1], With[{p1 = RotationMatrix[theta1sol[t]].{0, -1}}, { Line[{{0, 0}, p1}], Disk[p1, 0.1], With[{p2 = p1 + RotationMatrix[theta2sol[t]].{0, -1}}, { Line[{p1, p2}], Disk[p2, 0.1] }] }] }, PlotRange -> {{-3, 3}, {-3, 1}} ], {t, 0, 10}, SaveDefinitions -> True ]
Wolfram Research (2015)，EntityInstance，Wolfram 语言函数，https://reference.wolfram.com/language/ref/EntityInstance.html.

文本

Wolfram Research (2015)，EntityInstance，Wolfram 语言函数，https://reference.wolfram.com/language/ref/EntityInstance.html.

CMS

Wolfram 语言. 2015. "EntityInstance." Wolfram 语言与系统参考资料中心. Wolfram Research. https://reference.wolfram.com/language/ref/EntityInstance.html.

APA

Wolfram 语言. (2015). EntityInstance. Wolfram 语言与系统参考资料中心. 追溯自 https://reference.wolfram.com/language/ref/EntityInstance.html 年

BibTeX

@misc{reference.wolfram_2026_entityinstance, author="Wolfram Research", title="{EntityInstance}", year="2015", howpublished="\url{https://reference.wolfram.com/language/ref/EntityInstance.html}", note=[Accessed: 14-September-2026]}

BibLaTeX

@online{reference.wolfram_2026_entityinstance, organization={Wolfram Research}, title={EntityInstance}, year={2015}, url={https://reference.wolfram.com/language/ref/EntityInstance.html}, note=[Accessed: 14-September-2026]}