feat(dsp): ensure that the findsignal() output is sorted by arrival time

src/dsp.jl

@@ -655,7 +655,8 @@ times are computed based on a matched filter. If it is set to `false`, an
 iterative optimization is performed to find more accruate arrival times.
 
 Returns named tuple `(time=t, amplitude=a)` where `t` is a vector of arrival
-times and `a` is a vector of complex amplitudes of the arrivals.
+times and `a` is a vector of complex amplitudes of the arrivals. The arrivals
+are sorted in ascending order of arrival times.
 
 # Examples:
 ```julia-repl
@@ -689,7 +690,8 @@ function findsignal(r, s, n=1; prominance=0.2, coarse=false)
   p = p[ndx]
   if coarse
     t = time(Float64.(p), s)
-    return (time=t, amplitude=samples(mfo[p]))
+    ndx = sortperm(t)
+    return (time=t[ndx], amplitude=samples(mfo[p[ndx]]))
   end
   # iterative fine arrival time estimation
   margin = 5   # arrival time may vary up to margin from coarse estimates
@@ -716,7 +718,8 @@ function findsignal(r, s, n=1; prominance=0.2, coarse=false)
   pp = v[1:length(p)] .+ i
   t = time(pp, s)
   a = complex.(v[length(p)+1:2*length(p)], v[2*length(p)+1:3*length(p)])
-  (time=t, amplitude=a)
+  ndx = sortperm(t)
+  (time=t[ndx], amplitude=a[ndx])
 end
 
 """

test/runtests.jl

@@ -637,6 +637,11 @@ end
   @test t ≈ [0.000775, 0.001545, 0.003124] atol=1e-5
   @test real(a) / real(a[1]) ≈ [1.0, -0.8, 0.6] atol=1e-2
 
+  y = compose(real(x), time([32.75, 64.25, 129.0], x), [0.8, -0.7, 1.0]; duration=0.2)
+  t, a = findsignal(x, y, 3; coarse=false)
+  @test t ≈ [0.000775, 0.001545, 0.003124] atol=2e-6
+  @test real(a) / real(a[3]) ≈ [0.8, -0.7, 1.0] atol=1e-2
+
   @test delay!([1,2,3,4], -1) == [2,3,4,0]
   @test delay!([1,2,3,4], 1) == [0,1,2,3]