Overbar in annotation textbox in Matlab plot (using Latex as interpreter)

Question

I am trying to do write a simple equation of a plane plus the value of the coefficient \bar{a}_1, a_2 and a_3 but I cannot get the \bar to work. Any suggestion? I tried $\bar{a}_{1}$ with or without dollars, everything else looks fine to me, I used latex or tex interpreter but it cannot recognize it. this is the code:

a1=1
a2=2
a3=3
str = {'LLSQ fit:','z=$\bar{a}_{1}$+a_2x+a_3y',sprintf('$\bar{a}_{1}$=%5.2f',a1),sprintf('a_2=%5.2f',a2),sprintf('a_3=%5.2f',a3)};
annH = annotation('textbox',[0.63 0.8 0.08 0.08],'string',str,'interpreter','latex')
set(annH,'FitBoxToText','on','fontsize', 18,'BackgroundColor',[1 1 1])  

thanks

Answer 1

I have listed the problems with your code below, here is a working code:

str = {'LLSQ fit: ' ...
    'z = $\bar{a}_{1}$ + $a_2x$ + $a_3y$' ...
    ['$\bar{a}_{1}$ = ' sprintf('%5.2f', a1)] ...
    ['$a_2$ = ' sprintf('%5.2f', a2)] ...
    ['$a_3$ = ' sprintf('%5.2f', a3)]};

annotation('textbox', [0.5 0.8 0.3 0.08], 'interpreter','latex', 'String', str);

Problems with the original code

1. You have to wrap the whole latex commands with $ sign:

   This code does not give the desired output:

   annotation('textbox', [.2 .4 .1 .1], 'interpreter','latex', 'String', 'a_2x');
   

   But this one does:

   annotation('textbox', [.2 .4 .1 .1], 'interpreter','latex', 'String', '$a_2x$');
   

2. You will loose some part of the string if you use sprintf since it has another interpreter (there are workarounds for this, but I suggest concatenating strings as I did above)

   sprintf('$\bar{a}_{1}$ = %5.2f', a1)
   

   will return:

   ar{a}_{1}$ = 1.00
   

   which is not recognized by latex. (\b is interpreted as backspace in sprintf and removes the vital $ sign.)