Fix #30; equal elements for a plateau must occur after the candidate …

…extrema
halleysfifthinc · Jul 31, 2023 · 077381a · 077381a
1 parent 2d526c1
commit 077381a
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Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/src/minmax.jl b/src/minmax.jl
@@ -18,15 +18,21 @@ function findnextextrema(cmp, x::AbstractVector, i::Int, w::Int, strict::Bool)
                     peak &= false
                     i = j > i ? j : i + 1
                     break # No reason to continue checking if the rest of the elements qualify
-                elseif xi === xj # plateau
+                elseif xi === xj # potential plateau
                     k = findnext(p -> xi !== p, x, j+1)
                     # @show k i j
                     if strict
                         if !isnothing(k) && i-1 ≥ firstindex(x)
                             xi1 = x[i-1]
                             xk = x[k]
                             # @show xi1 xi xk i j k
-                            if !ismissing(xi1) && !isnan(xi1) && cmp(xi1, xi) &&
+                            if k < i
+                                # elements of equal value are allowed within x[i-w:i+w] when
+                                # `strict == true` (as long as the immediately previous
+                                # element is less than `x[i]`, etc as tested on the next
+                                # line)
+                                continue
+                            elseif !ismissing(xi1) && !isnan(xi1) && cmp(xi1, xi) &&
                                 !ismissing(xk) && !isnan(xk) && cmp(xk, xi)
                                 # plateau begins and ends with elements less than the current
                                 return i
@@ -44,7 +50,7 @@ function findnextextrema(cmp, x::AbstractVector, i::Int, w::Int, strict::Bool)
                     else
                         xk = isnothing(k) ? NaN : x[k]
                         xi1 = i-1 ≥ firstindex(x) ? x[i-1] : NaN
-                        if something(k, lastindex(x)+1) ≥ i+w &&
+                        if i+w ≤ something(k, lastindex(x)+1) &&
                             (ismissing(xi1) || isnan(xi1) || cmp(xi1, xi)) &&
                             (ismissing(xk) || isnan(xk) || cmp(xk, xi))
                             return i

diff --git a/test/minmax.jl b/test/minmax.jl
@@ -83,6 +83,10 @@ x1 = a*sin.(2*pi*f1*T*t)+b*sin.(2*pi*f2*T*t)+c*sin.(2*pi*f3*T*t);
         # issue #4
         @test isempty(argmaxima(zeros(10)))
         @test argmaxima(zeros(10), 1; strict=false) == [1]
+
+        # issue #30
+        y = [12.452637, 12.389122, 12.452637, 12.512817, 48.756142, 48.410103, 45.00222]
+        @test findnextmaxima(y, 3, 2) === 5
     end
 
     # A missing or NaN should not occur within the `w` of the peak