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2e5257372b
Because certain aggregates and concatenation requires results in
a certain order, this change allows specific control of the order
features are added to the aggregate during an expression evaluation.
E.g.
concatenate("Station",concatenator:=',', order_by:="Station")
will give a comma separated list of station names in alphabetical
order, rather than layer feature order.
Sponsored by SMEC/SJ
16 lines
902 B
Plaintext
16 lines
902 B
Plaintext
{
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"name": "concatenate_unique",
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"type": "function",
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"description": "Returns all unique strings from a field or expression joined by a delimiter.",
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"arguments": [
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{"arg":"expression", "description":"sub expression of field to aggregate"},
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{"arg":"group_by", "optional":true, "description":"optional expression to use to group aggregate calculations"},
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{"arg":"filter", "optional":true, "description":"optional expression to use to filter features used to calculate aggregate"},
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{"arg":"concatenator", "optional":true, "description":"optional string to use to join values"},
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{"arg":"order_by", "optional":true, "description":"optional expression to use to order features used to calculate aggregate"}
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],
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"examples": [
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{ "expression":"concatenate(\"town_name\",group_by:=\"state\",concatenator:=',')", "returns":"comma separated list of unique town_names, grouped by state field"}
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]
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}
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