Help with "While" loop, not sure what I'm doing

I have started learning to use Matlab, I have a program that a colleague of mine has written for processing my data and I can't figure out why some of the script is not working. In the following loop, the first equation (RHlsun) uses the original value of glsuni istead of the new value from the loop. I hope this makes sense. What am I doing wrong?

counter  = 0;
glsuni = 0.5;
glsun = 0.0;

converge1 = abs(glsuni - glsun);

while converge1>0.0005;

      RHlsun = 1 - (1 - (RH / 100)) .* (((2 * glsuni * ((fgreen * fdry) / fstomata)) .* gvl .* (gbc ./ LAIsun)) ./ ((2 * glsuni .* ((fgreen * fdry) / fstomata)) .* ((2 * glsuni .* ((fgreen * fdry) / fstomata)) .* gvl + (2 * glsuni .* ((fgreen * fdry) / fstomata)) .* (gbc ./ LAIsun) + gvl .* (gbc ./ LAIsun))));
      sRHlsun = (sqrt((RHlsun.^2) + (RHlmin^2))) ./ (sqrt(1 + (RHlmin^2)));
      CO2lsun = CO2i - (CO2i - CO2a) * (((2 * 0.625 * glsuni * ((fgreen * fdry) / fstomata)) .* gcl .* (gbc ./ LAIsun)) ./ ((2 * 0.625 * glsuni * ((fgreen * fdry) / fstomata)) .* ((2 * 0.625 * glsuni .* ((fgreen * fdry) / fstomata)) .* gcl + (2 * 0.625 * glsuni * ((fgreen * fdry) / fstomata)) .* (gbc ./ LAIsun) + gcl .* (gbc ./ LAIsun))));
      glsun = mBWB .* ((Ansun .* sRHlsun) ./ CO2lsun) + bBWB;
      counter = counter + 1;
      converge1 = abs(glsuni - glsun);
      glsuni = glsun;

       if counter > 30;
           break;
       end;
  end;

[Nirmal]

What is the problem that you are having?

[Tom]

That equation is processed before the counter=counter+1 line, so maybe move the counter to the top of the loop?

Answer 1

[Jan]

Start with a simplification of the code:

counter  = 0;
glsuni   = 0.5;
glsun    = 0.0;
converge = abs(glsuni - glsun);

c1 = (fgreen * fdry) / fstomata;
c4 = gbc ./ LAIsun;
while converge > 0.0005 || counter > 30
   c2 = 2 * glsuni * c1;
   c3 = c2 * 0.625;

     RHlsun   = 1 - (1 - (RH / 100)) ./ (c2 ./ c4 + c2 ./ gvl + 1);
     sRHlsun  = sqrt(RHlsun .^ 2 + RHlmin ^ 2) ./ sqrt(1 + RHlmin ^ 2);
     CO2lsun  = CO2i - (CO2i - CO2a) ./ (c3 ./ c4 + c3 ./ gcl + 1);
     glsun    = mBWB .* Ansun .* sRHlsun ./ CO2lsun + bBWB;
     converge = abs(glsuni - glsun);
     glsuni   = glsun;

     counter = counter + 1;
  end

Perhaps this allows you to see the problem by your own.