ENH: Add sample function for DataFrames

src/DataFrames.jl

@@ -70,6 +70,7 @@ export @~,
        readtable,
        rename!,
        rename,
+       sample,
        showcols,
        stack,
        stackdf,
@@ -111,7 +112,9 @@ for (dir, filename) in [
         ("statsmodels", "statsmodel.jl"),
 
         ("", "RDA.jl"),
-        ("", "deprecated.jl")
+        ("", "deprecated.jl"),
+
+        ("other", "sample.jl"),
     ]
 
     include(joinpath(dir, filename))

src/other/sample.jl

@@ -0,0 +1,31 @@
+import StatsBase: sample
+
+"""
+    sample(df[, n; replace=true, ordered=false])
+
+Draw a random sample of `n` rows from a data frame `df` and return the result as a data frame.
+
+# Arguments
+
+- `replace::Bool=true`: Should sampling be performed with replacement?
+- `ordered::Bool=false`: Should an ordered sample be taken?
+
+# Example
+```
+julia> using RDatasets
+julia> iris = dataset("datasets", "iris")
+julia> srand(1)
+julia> sample(iris, 5)
+5×5 DataFrames.DataFrame
+│ Row │ SepalLength │ SepalWidth │ PetalLength │ PetalWidth │ Species      │
+|-----|-------------|------------|-------------|------------|--------------|
+│ 1   │ 5.0         │ 2.0        │ 3.5         │ 1.0        │ "versicolor" │
+│ 2   │ 6.2         │ 2.9        │ 4.3         │ 1.3        │ "versicolor" │
+│ 3   │ 6.7         │ 3.1        │ 4.7         │ 1.5        │ "versicolor" │
+│ 4   │ 5.5         │ 2.3        │ 4.0         │ 1.3        │ "versicolor" │
+│ 5   │ 5.8         │ 2.7        │ 5.1         │ 1.9        │ "virginica"  │
+```
+"""
+function sample(df::AbstractDataFrame, n::Integer=1; replace::Bool=true, ordered::Bool=false)
+    df[sample(1:size(df, 1), n, replace=replace, ordered=ordered), :]
+end

test/runtests.jl

@@ -27,7 +27,8 @@ my_tests = ["utils.jl",
             "iteration.jl",
             "duplicates.jl",
             "show.jl",
-            "statsmodel.jl"]
+            "statsmodel.jl",
+            "sample.jl"]
 
 println("Running tests:")
 

test/sample.jl

@@ -0,0 +1,10 @@
+module TestSample
+    using Base.Test
+    using DataFrames
+
+    df = DataFrame(A=1:10,B=11:20)
+    srand(1)
+    df_sample = sample(df, 5)
+    @test df_sample[:A] == [1,8,7,4,2]
+    @test df_sample[:B] == [11,18,17,14,12]
+end