diff --git a/gravimeter/align.m b/gravimeter/align.m
new file mode 100644
index 0000000..da0a06b
--- /dev/null
+++ b/gravimeter/align.m
@@ -0,0 +1,15 @@
+function [A] = align(V)
+%A!ALIGN(V) returns a constat matrix A which is the real alignment of the
+%INVERSE of the complex input matrix V
+%from Mohit slides
+
+    if (nargin ==0) || (nargin > 1)
+        disp('usage: mat_inv_real = align(mat)')
+        return
+    end
+
+    D = pinv(real(V'*V));
+    A = D*real(V'*diag(exp(1i * angle(diag(V*D*V.'))/2)));
+
+
+end
diff --git a/gravimeter/pzmap_testCL.m b/gravimeter/pzmap_testCL.m
new file mode 100644
index 0000000..f148bff
--- /dev/null
+++ b/gravimeter/pzmap_testCL.m
@@ -0,0 +1,34 @@
+function [] = pzmap_testCL(system,H,gain,feedin,feedout)
+% evaluate and plot the pole-zero map for the closed loop system for
+% different values of the gain
+
+    [~, n] = size(gain);
+    [m1, n1, ~] = size(H);
+    [~,n2] = size(feedin);
+
+    figure
+    for i = 1:n
+        %     if n1 == n2
+        system_CL = feedback(system,gain(i)*H,feedin,feedout);
+
+        [P,Z] = pzmap(system_CL);
+        plot(real(P(:)),imag(P(:)),'x',real(Z(:)),imag(Z(:)),'o');hold on
+        xlabel('Real axis (s^{-1})');ylabel('Imaginary Axis (s^{-1})');
+        %         clear P Z
+        %     else
+        %         system_CL = feedback(system,gain(i)*H(:,1+(i-1)*m1:m1+(i-1)*m1),feedin,feedout);
+        %
+        %         [P,Z] = pzmap(system_CL);
+        %         plot(real(P(:)),imag(P(:)),'x',real(Z(:)),imag(Z(:)),'o');hold on
+        %         xlabel('Real axis (s^{-1})');ylabel('Imaginary Axis (s^{-1})');
+        %         clear P Z
+        %     end
+    end
+    str = {strcat('gain = ' , num2str(gain(1)))};  % at the end of first loop, z being loop output
+    str = [str , strcat('gain = ' , num2str(gain(1)))]; % after 2nd loop
+    for i = 2:n
+        str = [str , strcat('gain = ' , num2str(gain(i)))]; % after 2nd loop
+        str = [str , strcat('gain = ' , num2str(gain(i)))]; % after 2nd loop
+    end
+    legend(str{:})
+end