%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  Pcm7.m  -  Determines Epstein loss given value of B
%             Used by tranmag.m
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function y = Pcm7(Bx)
% B-Wlb values that follow are valid for M-7,0.014",60 Hz
b=[0 10 20 30 40 60 80 100 120 140 180 210]*1000;
wlb=[0 0.0082 0.033 0.073 0.125 0.26 0.455 0.78 1.35 ...
      1.84 3.04 4.13];
B=[0:210]*1000; Wlb=spline(b,wlb,B);
% Activate to plot B-Wlb curve
% m=101; plot(Wlb(1:m),B(1:m)); grid; pause; % Linear plot
% m=101; semilogx(Wlb(2:m),B(2:m)); grid; pause; % Semilog plot
n=length(B); k=0;
if Bx==0; k=-1; y=0; end
if Bx<0; k=-1; y=0; disp('WARNING - Bx < 0, Wlb = 0 returned'); end
if Bx>B(n); y=Wlb(n); k=-1; disp('CAUTION - Beyond B-Wlb curve');end
for i=1:n
if k==0 & (Bx-B(i))<=0; k=i; break; end
end
if k>0;
y=Wlb(k-1)+(Bx-B(k-1))/(B(k)-B(k-1))*(Wlb(k)-Wlb(k-1));
else;
end