ENH: Add sample function for DataFrames #997

s-celles · 2016-06-14T10:55:37Z

diegozea · 2016-06-14T13:48:22Z

src/other/sample.jl

+"""
+    sample(df[, N])
+
+Returns a (random) sample of a DataFrame


I prefer something like "Returns a (random) sample of rows from a DataFrame" to be explicit about the selección of rows.

+1, but say "of N rows".

diegozea · 2016-06-14T14:17:03Z

Thanks for doing this @scls19fr ! :) Test are missing, It would be great to have some tests for this functions.

nalimilan · 2016-06-14T18:47:25Z

src/other/sample.jl

+```
+julia> using RDatasets
+julia> iris = dataset("datasets", "iris")
+julia> sample(iris, 5)


Please add a call to srand(1) to ensure the results are always the same.

nalimilan · 2016-06-14T18:53:12Z

Thanks. Please add tests for the new feature, and add the function to the list of exports.

s-celles · 2016-06-14T19:12:18Z

I haven't add sample to utils.jl but to sample.jl because AbstractDataFrame must be defined before using them

nalimilan · 2016-06-14T19:42:21Z

src/other/sample.jl

@@ -0,0 +1,29 @@
+import StatsBase: sample
+
+function sample(df::AbstractDataFrame; replace::Bool=true, ordered::Bool=false)


Just do N::Integer=1 in the definition below, and you'll get this one for free.

nalimilan · 2016-06-15T16:39:28Z

src/other/sample.jl

+"""
+    sample(df[, n])
+
+Draw a random sample of `n` rows from a data frame `df` and return the result as a data frame


Missing ending dot.

nalimilan · 2016-09-05T08:27:08Z

Any opinions about the opportunity of adding this function?

ararslan · 2016-09-05T17:47:16Z

src/other/sample.jl

+│ 5   │ 5.8         │ 2.7        │ 5.1         │ 1.9        │ "virginica"  │
+```
+"""
+function sample(df::AbstractDataFrame, n::Integer=1; replace::Bool=true, ordered::Bool=false)


Should extend the function from StatsBase, i.e. function StatsBase.sample(...)

quinnj · 2017-09-07T18:02:12Z

I think this could be useful, but needs a rebase.

bkamins · 2019-07-24T14:30:55Z

I am closing this since we removed StatsBase.jl dependency in DataFrames.jl.

Given the relation of cost of materializing a DataFrame vs. cost of sampling I think it is easy enough to use df[sample(something selecting rows), :] even if this is suboptimal performance wise (the difference will not be noticeable).

Please reopen if you disagree.

nalimilan · 2019-07-25T13:44:31Z

It would still be kind of nice to be able to do sample(df, n) at some point. Maybe we could define sample in DataAPI, just like we do for describe. EDIT: and then we could have a generic definition in Tables.jl.

bkamins · 2019-07-25T13:48:56Z

Exactly, DataFrame is not specific here and we will delegate all the work to StatsBase.jl sample anyway.

anandijain · 2019-10-01T21:17:21Z

What about for groupby objects?

groups = groupby(df, :A)
I think it would be nice to be able to sample(groups, 3) and get three of the groups.

bkamins · 2019-10-02T07:14:17Z

There are two issues here:

The question is we want GroupedDataFrame to be a subtype of AbstractVector.
@nalimilan - what is your current status of thinking about it?
In general such sampling is not allowed as it would possibly produce duplicates in sample(groups, 3) and GroupedDataFrame does not allow for duplicate groups (and I think it should not allow for this).

In short to sample subgroups now you should write sample(collect(groups), 3) and probably this will stay this way.

nalimilan · 2019-10-02T17:27:58Z

IIRC we concluded that subtyping AbstractVector wasn't a good idea at least at this point. And indeed you're right that duplicating groups would be problematic.

bkamins · 2019-10-02T19:34:33Z

Thank you. I just wanted to make sure with AbstractVector status (and I agree).

diegozea reviewed Jun 14, 2016
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nalimilan reviewed Jun 14, 2016
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s-celles force-pushed the master branch from 387ca03 to 1604120 Compare June 14, 2016 19:10

s-celles force-pushed the master branch from a8c6ad0 to 0dc6c21 Compare June 14, 2016 19:16

nalimilan reviewed Jun 14, 2016
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s-celles force-pushed the master branch 3 times, most recently from 86b4c36 to dc436ee Compare June 15, 2016 05:54

nalimilan reviewed Jun 15, 2016
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ENH: Add sample function for DataFrames

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s-celles force-pushed the master branch from 4b17778 to 4b087e5 Compare June 15, 2016 16:55

s-celles mentioned this pull request Jun 28, 2016

Allow failures #1000

Closed

Update sample.jl

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nalimilan closed this Sep 5, 2016

nalimilan reopened this Sep 5, 2016

ararslan reviewed Sep 5, 2016
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quinnj mentioned this pull request Sep 7, 2017

Add ablity to sample a dataframe #676

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bkamins mentioned this pull request Jan 15, 2019

DataFrames.jl roadmap #1678

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bkamins closed this Jul 24, 2019

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ENH: Add sample function for DataFrames #997

ENH: Add sample function for DataFrames #997

s-celles commented Jun 14, 2016

diegozea Jun 14, 2016

nalimilan Jun 14, 2016

diegozea commented Jun 14, 2016

nalimilan Jun 14, 2016

nalimilan commented Jun 14, 2016

s-celles commented Jun 14, 2016

nalimilan Jun 14, 2016

nalimilan Jun 15, 2016

nalimilan commented Sep 5, 2016

ararslan Sep 5, 2016

quinnj commented Sep 7, 2017

bkamins commented Jul 24, 2019

nalimilan commented Jul 25, 2019 •

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bkamins commented Jul 25, 2019

anandijain commented Oct 1, 2019

bkamins commented Oct 2, 2019

nalimilan commented Oct 2, 2019

bkamins commented Oct 2, 2019

		@@ -0,0 +1,29 @@
		import StatsBase: sample

		function sample(df::AbstractDataFrame; replace::Bool=true, ordered::Bool=false)

ENH: Add sample function for DataFrames #997

ENH: Add sample function for DataFrames #997

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