Wolfram Language

Core Language

Pattern Matching with Associations

Version 11 introduces several functions to simplify the manipulation and pattern matching of associations.

Use KeyMemberQ and KeyFreeQ to test whether or not a key is part of an association.

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KeyMemberQ[<|a -> 1, b -> 2, c -> 3|>, a]
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KeyFreeQ[<|a -> 1, b -> 2, c -> 3|>, a]
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KeyValuePattern allows you to match a complete association that contains one or more given rules.

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MatchQ[<|a -> 1, b -> 2, c -> 3|>, KeyValuePattern[b -> _]]
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MatchQ[<|a -> 1, b -> 2, c -> 3|>, KeyValuePattern[{c -> _, a -> _}]]
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Compute data on the gravitational field at several points of the Earth.

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points = {{40, -100, 691}, {30, -120, 560}, {80, 70, 91}}; data = GeogravityModelData /@ points
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Select the cases for which the field magnitude is larger than the standard average value.

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Cases[data, KeyValuePattern[ "Magnitude" -> _?(GreaterThan[ Quantity[1, "StandardAccelerationOfGravity"]])]]
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Use KeyValueMap to further process each key-value pair.

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Cases[data, KeyValuePattern[ "Magnitude" -> _?(GreaterThan[ Quantity[1, "StandardAccelerationOfGravity"]])]]; KeyValueMap[ EntityProperty["GeogravityModel", #1] -> UnitConvert[#2, "Imperial"] &, First[%]]
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