hi , Im a beginner in using matlab , i tried several times to debug my program but the error is still the same!! can you help me please:) Thanks
clear clear all
global kfiler d kmatrice phi kmes kcalc y s Rcmin kcalcmin Rc kmatrice=[29.16;0;0;0;0]; kfiler=2000; d=91e-6;
kmes = [29.16;31.51;36.33;39.9;44.3];
phi = [0 0 0 0 0;0 7.4 0 0 0;0 0 11.52 0 0; 0 0 0 18.44 0;0 0 0 0 23.88];
kcalc=kmatrice*(2*kmatrice+(kfiler/(1+2*(kfiler*Rc/d)))-2*phi*(kmatrice-(kfiler/(1+2*(kfiler*Rc/d)))))/(2*kmatrice+(kfiler/(1+2*(kfiler*Rc/d)))+phi*(kmatrice-(kfiler/(1+2*(kfiler*Rc/d))))); y= (kmes-kcalc)^2;
s= @(Rc)sum(y); kcalcmin = fminsearch(s,kmatrice);
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Rc is empty (it gets initialised as a global variable but nothing is assigned to it), but it's used in your calc=... calculation.
Was this intentional?
The problem here is that anything multiplied by an empty  will return . And any non-empty matrix divided by an empty matrix will cause an error.
The final part of your calculation:
Is one such part. kfiler is not empty, but Rc (and consequently (1+2(kfiler*Rc/d))* is empty.
You'll get the same error if you type in:
100 / 
One small suggesion: break up your calculation into a few lines. Otherwise it will be a complete nightmare to debug because all error messages will point to this one huge line (which doesn't help you track them down)