MATLAB: How can fix index exceeds matrix error

Question

mn=input('Modül Giriniz:');
T=input('Teeth Numbers :');
at=input('Transverse pressure angle: ');
ad=input('Addendum Coef: ');
de=input('Deddendum Coef :');
Hobtip=input('Hob Tip Radius coef: ');
rg=mn*T/2;
rr=rg-(de*mn);
br=rg*cosd(at);
tr=rg+(ad*mn);
b=(tr-br)/180;
r=br;
a=1;
r2=num2cell(br:b:tr);
inva=tand(at)-(at*pi/180);
ctt1=pi*mn/2;
%                                     Involute Curves
while r<=tr
    r=r+b;
    a=a+1;
end
for i=1:1:a
    
    teta{i}=acosd(br/r2{i});
    invteta{i}=tand(teta{i})-(teta{i}*pi/180);
    ctt2{i}=2*r2{i}*((0.5*ctt1/rg)+inva-invteta{i});
    B{i}=0.5*ctt2{i}/r2{i};
    x{i}=r2{i}*sin( B{i});
    y{i}=r2{i}*cos(B{i});
    leftx{i}=-1*r2{i}*sin(B{i});
end
%                         Trochoid Curves
B_tr=(de*mn)-(Hobtip*mn);
L=(pi*mn/4.0)-(B_tr*tand(at))-(Hobtip*mn/(cosd(at)));
W=((((pi*mn)/2.0)-L)/rg);
E=0;
e=E;
Emax=50*pi/180;
tro=Emax/179;
o=1;
E2=num2cell(0:tro:Emax);
while (e<=Emax)
    e=e+tro;
    o=o+1;
end
for q=1:o
    Yz{q}=((rg-B_tr)*cos(E2{q}))+((rg*E2{q}*sin(E2{q})));
    
    Xz{q}=(rg*E2{q}*cos(E2{q}))-((rg-B_tr)*sin(E2{q}));
    
    DXZ{q}=(-(rg*E2{q}).*sin(E2{q}))+((B_tr*cos(E2{q})));
    
    DYZ{q}=(B_tr*sin(E2{q}))+((rg*E2{q})*cos(E2{q}));
    
    if(E==0)
        A{q}=90*pi/180.;
    end
    A{q}=atan(DXZ{q}./DYZ{q});
    
    Xt{q}=Xz{q}+((Hobtip*mn).*cos(A{q}));
    
    Yt{q}=Yz{q}-(Hobtip*mn.*sin(A{q}));
    
    Xtr{q}=Yt{q}.*sin(W)-Xt{q}.*cos(W);
    
    Ytr{q}=Yt{q}.*cos(W)+Xt{q}.*sin(W);
    leftXtr{q}=-1.*(Yt{q}.*sin(W)-Xt{q}.*cos(W));
end
%      Tooth Curves
% Involute ones
plot(cell2mat(x),cell2mat(y));
hold on
plot(cell2mat(leftx),cell2mat(y));
hold on
% Trochoid Ones
plot(cell2mat(Xtr),cell2mat(Ytr));
hold on
plot(cell2mat(leftXtr),cell2mat(Ytr));

Answer 1

Your first error occurs with teta{i} = acosd(br/r2{i}); because r2 has one less element than the max values of i. I would suggest initializing a as 0 instead of 1.

I did not encounter the other errors.