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The difference between A[" "] and EntityValue[A," "] in Real World Data?

Zhenyu Zeng
Posted 3 years ago

Hello, I once thought A[" "] equals to the EntityValue[A," "] in Real World Data in MMA, but I am wrong. As in the case below:

Entity["GeographicRegion", "Europe"]["Countries"]["Flag"]

I get countries' names.

But in 

EntityValue[Entity["GeographicRegion", "Europe"]["Countries"], "Flag"]

I will get countries' flags.

So what is the different between A[" "] and EntityValue[A," "] in Real World Data?
POSTED BY: Zhenyu Zeng
4 Replies
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Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago

Thanks for your patient explanation. I know how it works after reading it.

POSTED BY: Zhenyu Zeng
Eric Rimbey
Eric Rimbey
Posted 3 years ago
POSTED BY: Eric Rimbey
Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago

Hello,

  1. Why should I use EntityClass here?

  2. why

    EntityValue[Entity["Country", "France"], "Flag"]

equals to

Entity["Country", "France"]["Flag"]

but

Entity["GeographicRegion", "Europe"]["Countries"]["Flag"]

doesn't equal to 

EntityValue[Entity["GeographicRegion", "Europe"]["Countries"], "Flag"]
POSTED BY: Zhenyu Zeng
Eric Rimbey
Eric Rimbey
Posted 3 years ago

I get countries' names

No you don't. You get an expression that has a list of country names applied to the argument "Flag". Such an expression has no rewrite rule, so it remains unevaluated.

You could try this alternate:

EntityClass["Country", "Europe"]["Flag"]
POSTED BY: Eric Rimbey
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