Interp1 returning NaN for ode45

The interp1 function returns a NaN value for the time-dependent functions that are later introduced in the ode45 function. Using pchip or spline instead of interp1 returns a value other than NaN, but the solutions are not valid.

My code is the one that follows, thank you in advance.

function [T_V , W_V , x_V , y_V , h_V , Vfin] = viraje(x0 , y0 , h0 , W0 ,...
    V0 , Vf , gamma0 , gammaf , chi0 , chif , chip ,  CD0 , k , S , cE)

clc

g = 9.80665;   %m/s2

tfin = (chif - chi0)/chip;

gammap = (gammaf-gamma0)/tfin;
Vp     = (Vf-V0)/tfin;

t_interp = linspace(0 , tfin , 10);
V        = V0     + Vp*t_interp;
gamma    = gamma0 + gammap*t_interp;
mu       = atan(chip/g*V.*cos(gamma)./(V/g*gammap + cos(gamma)));
h        = Hviraje(t_interp , h0 , V0 , Vp , gamma0 , gammap);
rho      = densidad(h);

      function dWdt = dif(t,W,t_interp,V,gamma,mu,rho)

          if Vp == 0
              V = V0;
          else
              V = interp1(V,t_interp,t,'pchip');
          end

          if gammap == 0
              gamma = gamma0;
          else
              gamma = interp1(gamma,t_interp,t,'pchip');
          end

          if Vp == 0 && gammap == 0
              mu = mu(1);
          else
              mu = interp1(mu,t_interp,t,'pchip');
          end

          if gamma0 == 0 && gammap == 0
              rho = densidad(h0);
          else
              rho = interp1(rho,t_interp,t,'pchip');
          end

          dWdt  = -cE*(0.5*rho.*(V.^2)*S*CD0 + 2*k./(rho*S)*(chip*W.*cos(gamma)./...
              (g*sin(mu))).^2 + W.*sin(gamma) + Vp/g*W)

      end

tspan = [0 tfin];
ic    = W0;
[t,W] = ode45(@(t,W) dif(t,W,t_interp,V,gamma,mu,rho) , tspan , ic);

W_V = W;
h_V = Hviraje(t , h0 , V0 , Vp , gamma0 , gammap);
x_V = Xviraje(t , x0 , V0 , Vp , gamma0 , gammap , chi0 , chip);
y_V = Yviraje(t , y0 , V0 , Vp , gamma0 , gammap , chi0 , chip);

rho   = densidad(h_V)';
gamma = gamma0 + gammap*t;
V     = V0 + Vp*t;
mu    = atan(chip/g*V.*cos(gamma)./(V/g*gammap + cos(gamma)));

T_V   = 0.5*rho.*V.^2*S*CD0 + 2*k./(rho*S).*(chip*W.*cos(gamma)./...
    (g*sin(mu))).^2 + W.*sin(gamma) + Vp/g*W;

Vfin = Vf;

end

function H = Hviraje(T , h0 , V0 , Vp , gamma0 , gammap)

      syms h(t)
      eqn     = diff(h,t) == (V0 + Vp*t)*sin(gamma0 + gammap*t);
      cond    = h(0) == h0;
      ySol(t) = dsolve(eqn,cond);
      H       = ySol(T);

end

function X = Xviraje(T , x0 , V0 , Vp , gamma0 , gammap , chi0 , chip)

      syms x(t)
      eqn     = diff(x,t) == (V0 + Vp*t)*cos(gamma0 + gammap*t)*cos(chi0 + chip*t);
      cond    = x(0) == x0;
      ySol(t) = dsolve(eqn,cond);
      X       = ySol(T);

end

function Y = Yviraje(T , y0 , V0 , Vp , gamma0 , gammap , chi0 , chip)

      syms y(t)
      eqn     = diff(y,t) == (V0 + Vp*t)*cos(gamma0 + gammap*t)*sin(chi0 + chip*t);
      cond    = y(0) == y0;
      ySol(t) = dsolve(eqn,cond);
      Y       = ySol(T);

end

[Walter Roberson]

interp1() returns nan for most interpolation methods when you ask it to project at locations that are outside the range of the first parameter, unless you pass it the 'extrap' parameter.

Answer 1

[Bruno Luong]

V = interp1(V,t_interp,t,'pchip');

It looks arguments are swapped; I think it should be

V = interp1(t_interp,V,t,'pchip');

and similar for other INTERP1 calls.