fix integration

src/integration.jl

@@ -12,8 +12,13 @@ increment `h`
 """
 function integrate(y::ArrayOrSubArray{<:Real,1}, h::Real; method::Symbol=:simpson)::Real
     n = length(y) - 1
+    if n%2==1
+        println("warning: `y` length (number of intervals) must be odd, switching to first order integration.")
+        method=:trapezoid
+    end
+
     if method == :simpson
-        n % 2 == 0 || error("`y` length (number of intervals) must be odd")
+        # n % 2 == 0 || error("`y` length (number of intervals) must be odd")
         s = sum(y[1:2:n] + 4 * y[2:2:n] + y[3:2:n+1])
         return h / 3 * s
     elseif method == :trapezoid