[?] Get the value of an Entity's property ?

Questions
1

Hi,
I am trying to put into variable the value of the "region" of the "PhysicalSystem"'s "rectangular bar magnet"…without success, although it looks trivial.
EntityValue[] shows me that there is a "type" called "PhysicalSystem".

EntityValue[Entity["PhysicalSystem"],"Entities"]

is listing "rectangular bar magnet".

EntityValue[rectangular bar magnet	(physical system),"Properties"]

is listing the "region" property. Also the

EntityValue[rectangular bar magnet	(physical system),"PropertyAssociation"]

lists the region property value as:

EntityProperty["PhysicalSystem", "Region"] -> 
 Cuboid[{-(QuantityVariable["a","Length"]/2), -(QuantityVariable[
    "b","Length"]/2), -(QuantityVariable["c","Length"]/
    2)}, {QuantityVariable["a","Length"]/2, QuantityVariable[
   "b","Length"]/2, QuantityVariable["c","Length"]/2}]

However when I try to get that value directly with:

In[24]:= EntityProperty[rectangular bar magnet	(physical system),Entity[rectangular bar magnet	(physical system),region	(word)]]
Out[24]= EntityProperty[rectangular bar magnet,Entity[rectangular bar magnet,region]]

or

In[33]:= EntityValue[rectangular bar magnet	(physical system),Entity[rectangular bar magnet	(physical system),region	(word)]]
Out[33]= EntityValue[rectangular bar magnet,Entity[rectangular bar magnet,region]]

I am not getting the Cuboid. Any good advise is highly appreciated.
János

2

It’s hard to tell exactly what you’re doing, since you’re copying plain text instead of InputForm, which would be more helpful, but it looks to me like you’re a) not using any correct syntax to request a property value and b) somehow also including the “Word” type entity “region” instead of the “Region” property associated with physical systems. Any of these will get you what you want, I think:

(Local2) In[5]:= 
Entity["PhysicalSystem", "RectangularBarMagnet"]["Region"]

(Local2) Out[5]= Cuboid[{-(QuantityVariable["a","Length"]/2), -(
   QuantityVariable["b","Length"]/2), -(QuantityVariable[
   "c","Length"]/2)}, {QuantityVariable["a","Length"]/2, 
  QuantityVariable["b","Length"]/2, QuantityVariable["c","Length"]/2}]

(Local2) In[10]:= 
Entity["PhysicalSystem", "RectangularBarMagnet"][
 EntityProperty["PhysicalSystem", "Region"]]

(Local2) Out[10]= Cuboid[{-(QuantityVariable["a","Length"]/2), -(
   QuantityVariable["b","Length"]/2), -(QuantityVariable[
   "c","Length"]/2)}, {QuantityVariable["a","Length"]/2, 
  QuantityVariable["b","Length"]/2, QuantityVariable["c","Length"]/2}]

(Local2) In[6]:= EntityValue[
 Entity["PhysicalSystem", "RectangularBarMagnet"], "Region"]

(Local2) Out[6]= Cuboid[{-(QuantityVariable["a","Length"]/2), -(
   QuantityVariable["b","Length"]/2), -(QuantityVariable[
   "c","Length"]/2)}, {QuantityVariable["a","Length"]/2, 
  QuantityVariable["b","Length"]/2, QuantityVariable["c","Length"]/2}]

(Local2) In[9]:= EntityValue[
 Entity["PhysicalSystem", "RectangularBarMagnet"], 
 EntityProperty["PhysicalSystem", "Region"]]

(Local2) Out[9]= Cuboid[{-(QuantityVariable["a","Length"]/2), -(
   QuantityVariable["b","Length"]/2), -(QuantityVariable[
   "c","Length"]/2)}, {QuantityVariable["a","Length"]/2, 
  QuantityVariable["b","Length"]/2, QuantityVariable["c","Length"]/2}]
3

Alan,

Thanks a lot. Now I start to “see”. :slight_smile:
Best,
János