Index exceeds array bounds

Hi, I'm getting some errors and I'm not sure why. I got the second error after removing the code that held the first error. Any help is greatly appreciated.

Index exceeds array bounds
Error in Lambert (line 11)           if X1(1)*X2(2)-X1(2)*X2(1) < 0

and an

Index exceeds array bounds.
Error in Lambert (line 56)          V1(K)=(1/G)*(X2(K)-(F*X1(K)));

function [A,P,V1,V2,conv] = Lambert(X1,X2,TOF,mu,JJ,tol,kmax)
X1=input('departure radius: ');
X2=input('arrival radius: ');
TOF=input('time of flight: ');
mu=input('Gravitational parameter: ');
JJ=input('1 for ellipse, 0 otherwise');
tol=input('required tolerance: ');
kmax=input('max number of iterations');
conv = true;
ta = acos(dot(X1,X2)/(norm(X1)*norm(X2)));
if X1(1)*X2(2)-X1(2)*X2(1) < 0
    ta=2*pi-ta;
end
c = sqrt(norm(X1)^2 + norm(X2)^2 - 2*norm(X1)*norm(X2)*cos(ta));
s = (norm(X1)+norm(X2)+c)/2;
lambda = (sqrt(norm(X1)*norm(X2))*cos(ta/2))/s;
w = atan((norm(X2)/norm(X1))^0.25)-(pi/4);
l = ((tan(2*w))^2+(sin(ta/4))^2)/((tan(2*w))^2 + (sin(ta/4))^2 + cos(ta/2));
M = (8*mu*(TOF^2))/((s^3)*((1+lambda)^6));
x = 1;
y = 0;
if ~JJ
    x = 0.1E-13;
end
V1 = zeros(3,1);
V2 = zeros(3,1);
DX = 9e99;
k = 0;
while abs(DX) > tol
    n = x/(((sqrt(1+x))+1)^2);
    PHI = (8*(sqrt(1+x)+1))/(3+(1/(5+n+((9/7)*n)/(1+(((16/63)*n)/(1+(((25/99)*n)/(1+(((36/143)*n)/(1+(((49/195)*n)/(1+(((64/255)*n)/(1+(((81/323)*n)/(1+(100/399)*n))))))))))))))));
    H1 = ((l+x)^2*(1+3*x+PHI))/((1+2*x+l)*(4*x+PHI*(3+x)));
    H2 = (M*(x-l+PHI))/((1+2*x+l)*(4*x+PHI*(3+x)));
    B = (27*H2)/(4*((1+H1)^3));
    if B <= -1
        B = -1;
    end
    U = -B/(2*(sqrt(1+B)+1));
    KU = (1/3)/(1-(((4/27)*U)/(1-(((8/27)*U)/(1-(((2/9)*U)/(1-(((22/81)*U)/(1-(((208/891)*U)/(1-(((418/1755)*U)/(1-(((598/2295)*U)/(1-(700/2907)*U)))))))))))))));
    YNEW = ((1+H1)/3)*(2+(sqrt(1+B)/(1-(2*U*(KU^2)))));
    XNEW = sqrt(((1-l)/2)^2+(M/YNEW^2))-((1+l)/2);
    DX = abs(XNEW - x);
    x = XNEW;
    y = YNEW;
    k = k+1;
    if k > kmax
        conv = false;
        break
    end
end
A = M*s*(1+lambda)^2/(8*x*y^2);
P = (2*norm(X1)*norm(X2)*y^2*(1+x)^2*(sin(ta/2)^2))/(M*s*(1+lambda)^2);
F = 1-(norm(X2)/P)*(1-cos(ta));
G = norm(X1)*norm(X2)*sin(ta)/sqrt(mu*P);
FDOT = sqrt(mu/P)*tan(ta/2)*((1-cos(ta))/P-1/norm(X2)-1/norm(X1));
GDOT = 1-(norm(X1)/P)*(1-cos(ta));
for K=1:3
    V1(K)=(1/G)*(X2(K)-(F*X1(K)));
    V2(K)=FDOT*X1(K)+GDOT*V1(K);
end
end

Answer 1

[Walter Roberson]

You have

X1=input('departure radius: ');
X2=input('arrival radius: ');

It would be most natural for people to respond with a single value to each of those prompts, especially since "radius" is singular.

if X1(1)*X2(2)-X1(2)*X2(1) < 0

That assumes that X1(2) and X2(2) exist, which would require that the user had entered at least two values for each of the two prompts.