diff --git a/Project.toml b/Project.toml
index 1f75ef4..ba63f64 100644
--- a/Project.toml
+++ b/Project.toml
@@ -10,6 +10,7 @@ ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 FFTW = "7a1cc6ca-52ef-59f5-83cd-3a7055c09341"
 Flux = "587475ba-b771-5e3f-ad9e-33799f191a9c"
 KernelAbstractions = "63c18a36-062a-441e-b654-da1e3ab1ce7c"
+LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Polynomials = "f27b6e38-b328-58d1-80ce-0feddd5e7a45"
 SpecialPolynomials = "a25cea48-d430-424a-8ee7-0d3ad3742e9e"
 Tullio = "bc48ee85-29a4-5162-ae0b-a64e1601d4bc"
diff --git a/src/NeuralOperators.jl b/src/NeuralOperators.jl
index 303b80a..c82c06e 100644
--- a/src/NeuralOperators.jl
+++ b/src/NeuralOperators.jl
@@ -9,6 +9,7 @@ module NeuralOperators
     using ChainRulesCore
     using Polynomials
     using SpecialPolynomials
+    using LinearAlgebra
 
     include("utils.jl")
     include("polynomials.jl")
diff --git a/src/polynomials.jl b/src/polynomials.jl
index 8bee986..a7d2670 100644
--- a/src/polynomials.jl
+++ b/src/polynomials.jl
@@ -128,22 +128,25 @@ function chebyshev_ϕ_ψ(k)
 end
 
 function legendre_filter(k)
-    H0 = zeros(k, k)legendre
+    H0 = zeros(k, k)
     H1 = zeros(k, k)
     G0 = zeros(k, k)
     G1 = zeros(k, k)
     ϕ, ψ1, ψ2 = legendre_ϕ_ψ(k)
 
-    # roots = Poly(legendre(k, 2*x-1)).all_roots()
-    # x_m = np.array([rt.evalf(20) for rt in roots]).astype(np.float64)
-    # wm = 1/k/legendreDer(k,2*x_m-1)/eval_legendre(k-1,2*x_m-1)
+    l = convert(Polynomial, gen_poly(Legendre, k))
+    x_m = roots(l(Polynomial([-1, 2])))  # 2x-1
+    m = 2 .* x_m .- 1
+    wm = 1 ./ k ./ legendre_der.(k, m) ./ gen_poly(Legendre, k-1).(m)
     
-    # for ki in range(k):
-    #     for kpi in range(k):
-    #         H0[ki, kpi] = 1/np.sqrt(2) * (wm * phi[ki](x_m/2) * phi[kpi](x_m)).sum()
-    #         G0[ki, kpi] = 1/np.sqrt(2) * (wm * psi(psi1, psi2, ki, x_m/2) * phi[kpi](x_m)).sum()
-    #         H1[ki, kpi] = 1/np.sqrt(2) * (wm * phi[ki]((x_m+1)/2) * phi[kpi](x_m)).sum()
-    #         G1[ki, kpi] = 1/np.sqrt(2) * (wm * psi(psi1, psi2, ki, (x_m+1)/2) * phi[kpi](x_m)).sum()
+    for ki in 0:(k-1)
+        for kpi in 0:(k-1)
+            H0[ki+1, kpi+1] = 1/sqrt(2) * sum(wm .* ϕ[ki+1].(x_m/2) .* ϕ[kpi+1].(x_m))
+            G0[ki+1, kpi+1] = 1/sqrt(2) * sum(wm .* ψ(ψ1, ψ2, ki, x_m/2) .* ϕ[kpi+1].(x_m))
+            H1[ki+1, kpi+1] = 1/sqrt(2) * sum(wm .* ϕ[ki+1].((x_m.+1)/2) .* ϕ[kpi+1].(x_m))
+            G1[ki+1, kpi+1] = 1/sqrt(2) * sum(wm .* ψ(ψ1, ψ2, ki, (x_m.+1)/2) .* ϕ[kpi+1].(x_m))
+        end
+    end
 
     zero_out!(H0)
     zero_out!(H1)
diff --git a/src/utils.jl b/src/utils.jl
index ae64aa1..994fa75 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -7,8 +7,8 @@ function ϕ_(ϕ_coefs; lb::Real=0., ub::Real=1.)
 end
 
 function ψ(ψ1, ψ2, i, inp)
-    mask = (inp ≤ 0.5) * 1.0
-    return ψ1[i](inp) * mask + ψ2[i](inp) * (1-mask)
+    mask = (inp .> 0.5) .* 1.0
+    return ψ1[i+1].(inp) .* mask .+ ψ2[i+1].(inp) .* mask
 end
 
 zero_out!(x; tol=1e-8) = (x[abs.(x) .< tol] .= 0)
@@ -35,3 +35,13 @@ function proj_factor(a, b; complement::Bool=false)
     proj_ = sum(prod_ ./ r .* s)
     return proj_
 end
+
+_legendre(k, x) = (2k+1) * gen_poly(Legendre, k)(x)
+
+function legendre_der(k, x)
+    out = 0
+    for i in k-1:-2:-1
+        out += _legendre(i, x)
+    end
+    return out
+end
diff --git a/test/polynomials.jl b/test/polynomials.jl
index 09fb11d..1163b7e 100644
--- a/test/polynomials.jl
+++ b/test/polynomials.jl
@@ -64,4 +64,46 @@
         @test ψ2[3](1) ≈ -1.0941547380212384
         @test ψ2[3](2) ≈ 0.
     end
+
+    @testset "legendre_filter" begin
+        H0, H1, G0, G1, Φ1, Φ2 = NeuralOperators.legendre_filter(3)
+
+        @test H0 ≈ [0.70710678  0.         0.       ;
+                   -0.61237244  0.35355339 0.       ;
+                    0.         -0.6846532  0.1767767]
+        @test H1 ≈ [0.70710678 0.         0.       ;
+                    0.61237244 0.35355339 0.       ;
+                    0.         0.6846532  0.1767767]
+        @test G0 ≈ [0.35355339 0.61237244 0.        ;
+                    0.         0.1767767  0.6846532 ;
+                    0.         0.         0.70710678]
+        @test G1 ≈ [-0.35355339 0.61237244 0.        ;
+                    0.         -0.1767767  0.6846532 ;
+                    0.          0.        -0.70710678]
+        @test Φ1 == I(3)
+        @test Φ2 == I(3)
+    end
+
+    @testset "chebyshev_filter" begin
+        # H0, H1, G0, G1, Φ1, Φ2 = NeuralOperators.chebyshev_filter(3)
+
+        # @test H0 ≈ [0.70710678  0.          0.       ;
+        #            -0.5         0.35355339  0.       ;
+        #            -0.25       -0.70710678  0.1767767]
+        # @test H1 ≈ [0.70710678  0.          0.       ;
+        #             0.5         0.35355339  0.       ;
+        #            -0.25        0.70710678  0.1767767]
+        # @test G0 ≈ [0.60944614 0.77940383 0.        ;
+        #             0.66325172 1.02726613 1.14270252;
+        #             0.61723435 0.90708619 1.1562954 ]
+        # @test G1 ≈ [-0.60944614  0.77940383  0.       ;
+        #             0.66325172 -1.02726613  1.14270252;
+        #            -0.61723435  0.90708619 -1.1562954 ]
+        # @test Φ1 ≈ [1.         -0.40715364 -0.21440101;
+        #            -0.40715364  0.84839559 -0.44820615;
+        #            -0.21440101 -0.44820615  0.84002127]
+        # @test Φ2 ≈ [1.          0.40715364 -0.21440101;
+        #             0.40715364  0.84839559  0.44820615;
+        #            -0.21440101  0.44820615  0.84002127]
+    end
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 56eb498..ce3a602 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -4,6 +4,7 @@ using Flux
 using Polynomials
 using Zygote
 using CUDA
+using LinearAlgebra
 
 CUDA.allowscalar(false)