MATLAB: How to draw first order best fit in case of hold on figure

best fithold on fig

Hi everybody, I have used the following code, and get the fig as shown below.
x = [9.384,39.27];
Y1 = 6.49e-12 * x.^(-4); 
Y2 = 4.36e-10 * x.^(-5); 
Y3 = 1.69e-10 * x.^(-4.3);
loglog(x,Y1,'*') 
hold on
loglog(x,Y2,'*') 
hold on
loglog(x,Y3,'*') 
set(gca,'xtick',[9.384  39.27]);
set(gca,'xticklabel',{'A','B'});
Now I need to draw the best fit between A and B (best fit line draw from points at A towards points at B). I know the best fit in case of simple x and y plot, but due to hold on I do not know how to do this. Any guidance will be appreciated thanks.

Best Answer

Try this:
x = [9.384,39.27];
Y1 = 6.49e-12 * x.^(-4); 
Y2 = 4.36e-10 * x.^(-5); 
Y3 = 1.69e-10 * x.^(-4.3);
xv = reshape([x; x; x], [], 1);                     % Create X-Vector
YM = reshape([Y1; Y2; Y3], [], 1);                  % Create Y-Vector
DM = [xv(:) ones(size(xv(:)))];                     % Design Matrix
B = DM \ YM;                                        % Estimate Parameters
YFit = DM * B;                                      % Fit Regression For Plot
figure(1)
loglog(x,Y1,'*') 
hold on
loglog(x,Y2,'*') 
loglog(x,Y3,'*')
loglog(xv, YFit, '-r')                              % Plot Regression
hold off
set(gca,'xtick',[9.384  39.27]);
set(gca,'xticklabel',{'A','B'});
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