convert to double equation

my function gives an error while converting to double a one place (marked as %****) while at other places it works fine.

syms Y4(x)
syms Y1(x)
syms Y2(x)
syms Y5(x)
syms Y7(x)
syms Y3(x)
syms Y6(x)

sym =x 
syms a
syms b

v=input('velocity ');

cl=input('Cl ');
     
%to plot elliptical lift distribution
 w=input('total weight ');
 ws=input('half wing span ');
 
 disp(ws);
 b1=double(9.81*(4*(w/2))/(2*pi*ws));
 disp(b1);
 Y7(x)=(b1/(ws))*((ws^2-x^2))^0.5;
 disp(Y7(x));
 n=input('no of sections ');
 k=input('no. of tapered section');
for i=1:n
    m=0;
    c=0;
    cr=input('Root cord for that section ');
     ct=input('tip cord for that section ');
     l1=input('length of that section ' );
     
     L1=double((1.225*cl*(v^2)*cr)/2); %lift distribution per unit span
     L2=double((1.225*cl*(v^2)*ct)/2); 
     disp(L1);
     disp(L2);
     
     if cr==ct
         m=0;
         c=L1;
         if i==1 && k==1;
             Y1(x)=-(m/2)*x+(c/2); %linear lift eqn untapered section
         else n==3 && i==2;
             Y2(x)=-(m/2)*x+(c/2); %linear lift eqn untapered section
         end
     else
         
       
         if k==2
                     m=double((L1-L2)/l1);
                     c=L1;
                     Y1(x)=-(m/2)*x+(c/2); %linear lift eqn tapered section

         else
              l2=input('starting point of the taper section ');
        m=double((L1-L2)/l1);
        disp(m);
        c=L1+m*l2;
        disp(c);
                     Y3(x)=-(m/2)*x+(c/2);  %linear lift eqn tapered section

         end
     end
end


Y4(x)=Y1(x)+Y7(x); % schrenk eqn untapered section
Y5(x)=Y2(x)+Y7(x);       %schrenk eqn untapered section
Y6(x)=Y3(x)+Y7(x);   % schrenk eqn tapered section


%VIT schrenk eqn
% Y1=-0*x+33.037; 
% Y2=-27.10*x+37.02;
% Y4(x)=(-0*x+33.037/2 +(110.825*(0.1296-x^2)^0.5)/2);
% Y5(x)=((-27.10/2)*x+37.02/2 +(110.825*(0.1296-x^2)^0.5)/2);

xv=0;
I=[];
W1=input('length of first section ');
if n==3
    W2=input('length of 2nd section ');
end
if n==3
    
while xv(end)<= (ws+0.01) % to plot shear force with 3 sections
    if xv(end) <=W1
        I(end+1)=double(int(Y4,x,0,xv(end)));
    elseif   xv(end)>=W1 && xv(end)<=W2
      I(end+1)=double(int(Y5,x,0,xv(end)));
       else
        I(end+1)=double(int(Y6,x,0,xv(end)));  %****
     end
xv(end+1)=xv(end)+0.01;
end
else 
    while xv(end)<= (ws+0.01) % to plot shear force with 2 sections
        
    if xv(end) <=W1
        I(end+1)=double(int(Y4,x,0,xv(end)));
    else
        I(end+1)=double(int(Y6,x,0,xv(end)));
    end
    xv(end+1)=xv(end)+0.01;
    end
end
xv(end)=[];

xy=0;
a=0;

I2=int(Y4,a,x)
I4=int(Y5,a,x)
I5=int(Y6,a,x)


I3=[];
if n==3
    
while xy(end)<=(ws+0.01) % to plot BM with 3 sections
    if xy(end)<=W1                                                         
        
        I3(end+1)=double(int(I2,x,0,xy(end)));
        
    elseif  xy(end)>=W1 && xy(end)<=W2
           
             I3(end+1)=double(int(I4,x,0,xy(end)));
        
    else
         I3(end+1)=double(int(I5,x,0,xy(end)));
    end
    
    xy(end+1)=xy(end)+0.01;
    
end 
else
    while xy(end)<=(ws+0.01) % to plot BM witH 2 section
    if xy(end)<=W1
        
        I3(end+1)=double(int(I2,x,0,xy(end)));
    
    else
         I3(end+1)=double(int(I5,x,0,xy(end)));
         
    end
    
    xy(end+1)=xy(end)+0.01;
    
    end 
end
xy(end)=[];
plot(xy,I3);grid %BM graph
% plot(xv,I);grid %shear force graph

[RenatoL]

Can you include the error message in the question? That would really help.