MATLAB: Finite difference problem showing NaN value

finite differencematlab function

closed

When M>=2, in the last line of your code,

Rt_inc(M+1)=(v-1)*(rt_inc(M)^2)*((rt_inc(M+1)-rt_inc(M))/dt)/Sr(M);

because rt_inc(M+1)-rt_inc(M)=0 and Sr(M)=0, this becomes 0/0, which is not defined and produces a NaN in Matlab.

Here is one source of NaN's: In slipratio_fun with the initial value of t=0 and v=0, you have omega=v=0. The line

sx (abs(omega)*r>=abs(v)) = -1 + v./(omega.*r); % acceleration

sets sz equal to NaN because it's dividing by zero.

if all(isnan(A))
   A = B;
elseif all(isnan(B))
   B = A;
end
%proceed with A and B