--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/diracDiscr.m	Tue Nov 19 10:56:57 2019 -0800
@@ -0,0 +1,130 @@
+
+function d = diracDiscr(x_s, x, m_order, s_order, H)
+    % n-dimensional delta function
+    % x_s: source point coordinate vector, e.g. [x, y] or [x, y, z].
+    % x: cell array of grid point column vectors for each dimension.
+    % m_order: Number of moment conditions
+    % s_order: Number of smoothness conditions
+    % H: cell array of 1D norm matrices
+
+    dim = length(x_s);
+    d_1D = cell(dim,1);
+
+    % If 1D, non-cell input is accepted
+    if dim == 1 && ~iscell(x)
+        d = diracDiscr1D(x_s, x, m_order, s_order, H);
+
+    else
+        for i = 1:dim
+            d_1D{i} = diracDiscr1D(x_s(i), x{i}, m_order, s_order, H{i});
+        end
+
+        d = d_1D{dim};
+        for i = dim-1: -1: 1
+            % Perform outer product, transpose, and then turn into column vector
+            d = (d_1D{i}*d')';
+            d = d(:);
+        end
+    end
+
+end
+
+
+% Helper function for 1D delta functions
+function ret = diracDiscr1D(x_0in , x , m_order, s_order, H)
+
+m = length(x);
+
+% Return zeros if x0 is outside grid
+if(x_0in < x(1) || x_0in > x(end) )
+
+    ret = zeros(size(x));
+
+else
+
+    fnorm = diag(H);
+    eta = abs(x-x_0in);
+    tot = m_order+s_order;
+    S = [];
+    M = [];
+
+    % Get interior grid spacing
+    middle = floor(m/2);
+    h = x(middle+1) - x(middle);
+
+    poss = find(tot*h/2 >= eta);
+
+    % Ensure that poss is not too long
+    if length(poss) == (tot + 2)
+        poss = poss(2:end-1);
+    elseif length(poss) == (tot + 1)
+        poss = poss(1:end-1);
+    end
+
+    % Use first tot grid points
+    if length(poss)<tot && x_0in < x(1) + ceil(tot/2)*h;
+        index=1:tot;
+        pol=(x(1:tot)-x(1))/(x(tot)-x(1));
+        x_0=(x_0in-x(1))/(x(tot)-x(1));
+        norm=fnorm(1:tot)/h;
+
+    % Use last tot grid points
+    elseif length(poss)<tot && x_0in > x(end) - ceil(tot/2)*h;
+        index = length(x)-tot+1:length(x);
+        pol = (x(end-tot+1:end)-x(end-tot+1))/(x(end)-x(end-tot+1));
+        norm = fnorm(end-tot+1:end)/h;
+        x_0 = (x_0in-x(end-tot+1))/(x(end)-x(end-tot+1));
+
+    % Interior, compensate for round-off errors.
+    elseif length(poss) < tot
+        if poss(end)<m
+            poss = [poss; poss(end)+1];
+        else
+            poss = [poss(1)-1; poss];
+        end
+        pol = (x(poss)-x(poss(1)))/(x(poss(end))-x(poss(1)));
+        x_0 = (x_0in-x(poss(1)))/(x(poss(end))-x(poss(1)));
+        norm = fnorm(poss)/h;
+        index = poss;
+
+    % Interior
+    else
+        pol = (x(poss)-x(poss(1)))/(x(poss(end))-x(poss(1)));
+        x_0 = (x_0in-x(poss(1)))/(x(poss(end))-x(poss(1)));
+        norm = fnorm(poss)/h;
+        index = poss;
+    end
+
+    h_pol = pol(2)-pol(1);
+    b = zeros(m_order+s_order,1);
+
+    for i = 1:m_order
+        b(i,1) = x_0^(i-1);
+    end
+
+    for i = 1:(m_order+s_order)
+        for j = 1:m_order
+            M(j,i) = pol(i)^(j-1)*h_pol*norm(i);
+        end
+    end
+
+    for i = 1:(m_order+s_order)
+        for j = 1:s_order
+            S(j,i) = (-1)^(i-1)*pol(i)^(j-1);
+        end
+    end
+
+    A = [M;S];
+
+    d = A\b;
+    ret = x*0;
+    ret(index) = d/h*h_pol;
+end
+
+end
+
+
+
+
+
+