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Data Science Wolfram Language

How to add headers to a dataset?

Ehud Behar

Posted 1 year ago

Suppose I have the following dataset: dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}] How can I add a header `x` to the first column and a header `y` to the second column, so to get the following new dataset:? Dataset[{ <\|"x" -> 195, "y" -> 2.3\|>, <\|"x" -> 198, "y" -> 6.4\|>, <\|"x" -> 204, "y" -> -3.1\|> }] I am also looking for a command to assing units (cm and volts) to the values, so to get the following: Dataset[{ <\|"x" -> Quantity[195, "Centimeters"], "y" -> Quantity[2.3, "Volts"]\|>, <\|"x" -> Quantity[198, "Centimeters"], "y" -> Quantity[6.4, "Volts"]\|>, <\|"x" -> Quantity[204, "Centimeters"], "y" -> Quantity[-3.1, "Volts"]\|> }] Any ideas?

Suppose I have the following dataset:

dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}]

How can I add a header x to the first column and a header y to the second column, so to get the following new dataset:?

Dataset[{
  <|"x" -> 195, "y" -> 2.3|>,
  <|"x" -> 198, "y" -> 6.4|>,
  <|"x" -> 204, "y" -> -3.1|>
  }]

I am also looking for a command to assing units (cm and volts) to the values, so to get the following:

Dataset[{
  <|"x" -> Quantity[195, "Centimeters"], "y" -> Quantity[2.3, "Volts"]|>,
  <|"x" -> Quantity[198, "Centimeters"], "y" -> Quantity[6.4, "Volts"]|>,
  <|"x" -> Quantity[204, "Centimeters"], "y" -> Quantity[-3.1, "Volts"]|>
  }]

Any ideas?

POSTED BY: Ehud Behar

10 Replies

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Ehud Behar

Posted 2 months ago

Another way, if you start with raw numbers: list = {{195, 2.3}, {198, 6.4}, {204, -3.1}} Note that both `Thread[{"x", "y"} -> {195, 2.3}]` and `Thread[{"x", "y"} -> #] &[{195, 2.3}]` return {"x" -> 195, "y" -> 2.3} `Map` the pure function `Thread[{"x", "y"}->#]&` on every sub-list: Map[Thread[{"x", "y"} -> #] &, list] ({{"x" -> 195, "y" -> 2.3}, {"x" -> 198, "y" -> 6.4}, {"x" -> 204, "y" -> -3.1}}) and replace the head of each sub-list with that of Association: Apply[Association, Map[Thread[{"x", "y"} -> #] &, list], {1}] (or) Association @@@ Map[Thread[{"x", "y"} -> #] &, list] (* {<\|"x" -> 195, "y" -> 2.3\|>, <\|"x" -> 198, "y" -> 6.4\|>, <\|"x" -> 204, "y" -> -3.1\|>} *) Only thing left is to make this a `Dataset`: Dataset[%] Written as a single instruction: Association @@@ Map[Thread[{"x", "y"} -> #] &, list] // Dataset

Another way, if you start with raw numbers:

list = {{195, 2.3}, {198, 6.4}, {204, -3.1}}

Note that both Thread[{"x", "y"} -> {195, 2.3}] and Thread[{"x", "y"} -> #] &[{195, 2.3}] return

{"x" -> 195, "y" -> 2.3}

Map the pure function Thread[{"x", "y"}->#]& on every sub-list:

Map[Thread[{"x", "y"} -> #] &, list]
(*{{"x" -> 195, "y" -> 2.3}, {"x" -> 198, "y" -> 6.4}, {"x" -> 204, "y" -> -3.1}}*)

and replace the head of each sub-list with that of Association:

Apply[Association, Map[Thread[{"x", "y"} -> #] &, list], {1}]
(*or*)
Association @@@ Map[Thread[{"x", "y"} -> #] &, list]
(* {<|"x" -> 195, "y" -> 2.3|>, <|"x" -> 198, "y" -> 6.4|>, <|"x" -> 204, "y" -> -3.1|>} *)

Only thing left is to make this a Dataset:

Dataset[%]

Written as a single instruction:

Association @@@ Map[Thread[{"x", "y"} -> #] &, list] // Dataset

POSTED BY: Ehud Behar

Joshua Schrier

Joshua Schrier, Fordham University

Posted 1 year ago

Using a resource function... dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}]; ResourceFunction["DatasetWithHeaders"][ dataset, {"x", "y"}]

POSTED BY: Joshua Schrier

Vitaliy Kaurov

Vitaliy Kaurov, WOLFRAM Research

Posted 1 year ago

POSTED BY: Vitaliy Kaurov

Ehud Behar

Posted 1 year ago

Thanks very much. Regarding this instruction you wrote: dataset[All,Key["c"]/*<\|"ctotal"->Total,"clength"->Length\|>] Can you show me how to write it in a "FullForm" notatation, With explicit RightComposition? I am not so familiar with this infix shortcut and don't fully understand which expression is the argument of which function. Another question: You showed how to apply a function (`Total` and `Length`) on the values in each row. Suppose I want to add 3 to each value, or multiply each value by 2, in column `a`, how to do it?

POSTED BY: Ehud Behar

Hans Milton

Posted 1 year ago

For your second question, on adding units: dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}] Map[{Quantity[#[[1]],"Centimeters"],Quantity[#[[2]],"Volts"]}&,dataset//Normal]//Dataset

POSTED BY: Hans Milton

Eric Rimbey

Posted 1 year ago

Here's one way to start... dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}]; datasetWithHeader = dataset[All, Association @@ Thread[{"x", "y"} -> #] &] Then you could continue: datasetWithHeader[All, <\|"x" -> Quantity[#x, "Centimeters"], "y" -> Quantity[#y, "Volts"]\|> &]

Here's one way to start...

dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}];
datasetWithHeader = dataset[All, Association @@ Thread[{"x", "y"} -> #] &]

enter image description here

Then you could continue:

datasetWithHeader[All, <|"x" -> Quantity[#x, "Centimeters"], "y" -> Quantity[#y, "Volts"]|> &]

enter image description here

POSTED BY: Eric Rimbey

Ehud Behar

Posted 1 year ago

Very nice

POSTED BY: Ehud Behar

Eric Rimbey

Posted 1 year ago

Are you required to start with dataset = Dataset[{{195, 2.3}, {198, 6.4}, {204, -3.1}}] or do you have access to the raw data directly? E.g. data = {{195, 2.3}, {198, 6.4}, {204, -3.1}}