fix precision estimate

Author: baggepinnen

ext/ControlSystemIdentificationLSOptExt.jl

@@ -177,7 +177,8 @@ function _inner_pem(
     function Λ()
         resid = zeros(T * ny)
         J = ForwardDiff.jacobian(residuals!, resid, res.minimizer)
-        (T - length(p_guess)) * Symmetric(J' * J)
+        residuals!(resid, res.minimizer)
+        (T - length(p_guess)) / dot(resid, resid) * Symmetric(J' * J)
     end
 
     ukf = get_ukf(res.minimizer)

src/types.jl

@@ -172,6 +172,7 @@ hasinput(::OutputData)                           = false
 hasinput(::AbstractIdData)                       = true
 hasinput(::AbstractArray)                        = true
 hasinput(::ControlSystemsBase.LTISystem)             = true
+hasinput(::ControlSystemsBase.LTISystem{T}) where T  = true
 ControlSystemsBase.noutputs(d::AbstractIdData)       = obslength(getfield(d, :y))
 ControlSystemsBase.ninputs(d::AbstractIdData)        = hasinput(d) ? obslength(getfield(d, :u)) : 0
 ControlSystemsBase.nstates(d::AbstractIdData)        = 0