hello
FYI, you can access any figure underlying data (and of course compute the slope)
openfig('myfig.fig');
set(gcf, 'Visible','off')
Ax = gca; % Another Option
Lines = findobj(Ax, 'Type','line'); % Return Handles To All 'Line' Objects
x = Lines.XData(:); % Independent Variable (Force Column Vector With '(:)')
y = Lines.YData(:); % Dependent Variable (Force Column Vector With '(:)')
Figure_Table = table(x,y, 'VariableNames',{'X values','Y values'})