Remove rows from dataset using query

Question

MyDataSet[Select[#point[Fsr] == 1 &]] returns the row I want to delete, now I am trying what looks to me the most logic command to remove these rows, which is MyDataSet[Delete[#point[Fsr] == 1 &]] MyDataSet[DeleteCases[#point[Fsr] == 1 &]], but neither works .... any idea how this should be done?

Answer 1

Here's one way, not necessarily the most efficient:

MyDataSet[Select[#point[Fsr] == 1 & /* Not]]

Answer 2

There is a workaround if you use the named row style of Dataset (an association of associations) but don't actually apply Dataset to it. You can still perform querying as you can with a dataset but will have to explicitly use Query instead of it being implicitly used in the dataset[...] format.

assco = Association @@ 
 MapIndexed[First@#2 -> #1 &]@
   {<|"a" -> 5, "b" -> 2|>, <|"a" -> 3, "b" -> 2|>, <|"a" -> 5, "b" -> -1|>};

Here I have just indexed them with row number but you can use any expression. Now KeyDropFrom can be used with Select to drop the rows you are not interested in without making a new copy of the data. Below the rows with "a"-> 5 are dropped; the first and last row.

KeyDropFrom[assco, Keys@Select[#a == 5 &][assco]];
assco
(* <|2 -> <|"a" -> 3, "b" -> 2|>|> *)

The second row remains in assco with the others dropped.

Hope this helps.