diff --git a/src/TR.jl b/src/TR.jl
index 80ca581..5c3b68e 100644
--- a/src/TR.jl
+++ b/src/TR.jl
@@ -2,6 +2,88 @@
 
 
 
+
+"""
+Updates regression coefficient by solving the augmented TR problem [Xs; sqrt(lambda)*I] * beta = [ys; sqrt(lambda)*b_old]
+Note that many regularization types are supported but the regularization is on the difference between new and old reg. coeffs.
+and so most regularization types are probably not meaningful.
+
+Inputs:
+    - X/p       : Size of regularization matrix or data matrix (size of reg. mat. will then be size(X,2)
+    - regType   : "L2" (returns identity matrix)
+                  "bc" (boundary condition, forces zero on right endpoint for derivative regularization) or
+                  "legendre" (no boundary condition, but fills out reg. mat. with lower order polynomial trends to get square matrix)
+                  "std" (standardization, FILL OUT WHEN DONE)
+    - regParam1 : Int64, Indicates degree of derivative regularization (0 gives L\\_2)
+    - regParam2 : For regType=="plegendre" added polynomials are multiplied by sqrt(regParam2)
+
+Output
+"""
+function TRLooCVUpdate(X, y, lambdas, bold, regType="L2", regParam1=1, regParam2=1)
+
+n, p = size(X);
+mX   = mean(X, dims=1);    
+X    = X .- mX;
+my   = mean(y);    
+y    = y .- my;    
+    
+if regType == "bc"
+    regMat  = [I(p); zeros(regParam1,p)]; for i = 1:regParam1 regMat = diff(regMat, dims = 1); end
+elseif regType == "legendre"
+    regMat  = [I(p); zeros(regParam1,p)]; for i = 1:regParam1 regMat = diff(regMat, dims = 1); end
+    P, _    = plegendre(regParam-1, p);   
+    regMat[end-regParam1+1:end,:] = sqrt(regParam2) * P;
+elseif regType == "L2"
+    regMat = I(p);
+elseif regType == "std"
+    regMat = Diagonal(vec(std(X, dims=1)));
+elseif regType == "GL" # Grünwald-Letnikov fractional derivative regulariztion
+    # regParam1 is alpha (order of fractional derivative)
+    C = ones(p)*1.0;
+    for k in 2:p
+        C[k] = (1-(regParam1+1)/(k-1)) * C[k-1];
+    end
+
+    regMat = zeros(p,p);
+
+    for i in 1:p
+        regMat[i:end, i] = C[1:end-i+1];
+    end
+end
+    
+    
+X        = X / regMat;
+U, s, V  = svd(X, full=false)
+
+denom       = broadcast(.+, broadcast(./, lambdas, s'), s')'; 
+denom2      = broadcast(.+, ones(n), broadcast(./, lambdas', s.^2))
+resid       = broadcast(.-, y, U * (broadcast(./, s .* (U'*y), denom) + s .* broadcast(.-, 1, broadcast(./, 1, denom2)) .* (V' * bold)))
+H           = broadcast(.+, U.^2 * broadcast(./, s, denom), 1/n);
+rescv       = broadcast(./, resid, broadcast(.-, 1, H));
+press       = vec(sum(rescv.^2, dims=1));    
+rmsecv      = sqrt.(1/n .* press);
+GCV         = vec(broadcast(./, sum(resid.^2, dims=1), mean(broadcast(.-, 1, H), dims=1).^2));
+    
+idminPRESS  = findmin(press)[2][1]; # First index selects coordinates, second selects '1st coordinate'
+idminGCV    = findmin(GCV)[2][1]; # First index selects coordinates, second selects '1st coordinate'
+lambdaPRESS = lambdas[idminPRESS];
+lambdaGCV   = lambdas[idminGCV];
+    
+bcoeffs      = V * broadcast(./, (U' * y), denom);
+bcoeffs      = regMat \ bcoeffs;
+    
+if my != 0
+    bcoeffs = [my .- mX*bcoeffs; bcoeffs];
+end
+    
+bpress = bcoeffs[:, idminPRESS];
+bgcv   = bcoeffs[:, idminGCV];
+
+
+return bpress, bgcv, rmsecv, GCV, idminPRESS, lambdaPRESS, idminGCV, lambdaGCV
+end
+
+
 """
 ### TO DO: ADD FRACTIONAL DERIVATIVE REGULARIZATION <-- Check that it is correctly added:) ###
 
diff --git a/src/Ting.jl b/src/Ting.jl
index cf8e1e5..d4e6246 100644
--- a/src/Ting.jl
+++ b/src/Ting.jl
@@ -20,6 +20,7 @@ export importData
 export TRLooCV
 export TRSegCV
 export regularizationMatrix
+export TRLooCVUpdate
 
 include("convenience.jl")
 include("TR.jl")