I have the initial and boundary conditions: cond := ro(x, 0) = 0, v(x, 0) = 0, {ro(0, t) = 10, ro(40, t) = 20}, {v(0, t) = 10, v(40, t) = 20}; The PDE system is: sys2 := {diff(ro(x, t), t)+diff(ro(x, t)*v(x, t), x) = 0, diff(v(x, t), t)+v(x, t)*(diff(v(x, t), x))+3*ro(x, t)*(diff(ro(x, t), x)) = 0}; I use: sol1 := pdsolve(sys2, {cond}, numeric, time = t, range = 0 .. 40); values := sol1:-value(); ... When I try to see the values I receive the following error: values(40, 20); Error, (in solnproc) unable to compute solution for t>0.: column vector dimension less than length of sparse data