Fix uplo function (#730)

Author: bkamins

src/robust.jl

@@ -21,10 +21,9 @@ function uplo(x::AbstractVector; prop::Real=0.0, count::Integer=0)
     end
 
     # indices for lowest count values
-    x2 = copy(x)
-    lo = partialsort!(x2, 1:count+1)[end]
-    # indices for largest count values
-    up = partialsort!(x2, n-count:n)[1]
+    x2 = Base.copymutable(x)
+    lo = partialsort!(x2, count+1)
+    up = partialsort!(x2, n-count)
 
     up, lo
 end

test/robust.jl

@@ -1,5 +1,5 @@
 using StatsBase
-using Test
+using Test, Random
 
 ### Trimming outliers
 
@@ -53,3 +53,11 @@ using Test
 
 @test mean(trim([-Inf,1,2,3,4], count=1)) == 2
 @test mean(winsor([-Inf,1,2,3,4], count=1)) == 2
+
+Random.seed!(1234)
+for n in 2100:2120, c in 0:1000
+    x = randperm(n)
+    @test sort!(collect(winsor(x, count=c))) ==
+          reverse!(collect(winsor(n:-1:1, count=c))) ==
+          collect(winsor(1:n, count=c))
+end