NaNs are like wire coathangars, they multiply. Or perhaps evil zombies is a better description. They slime everything they touch, turning everything into new NaNs, propagating NaNs almost everywhere. Evil indeed. ;-)
For example, NaN plus ANYTHING = NaN.
NaN + 2
NaN times ANYTHING = NaN. Even zero.
NaN*0
So what did you do? You were hoping the trick of putting a test inline, that a multiply by zero would kill off the NaNs? Yeah, right. The zombies still survived.
Instead, you do have an option. Read the help for interp1!
x1=linspace(-pi,pi,20);
y1=sin(x1);
extrapval = 42;
f=@(x)interp1(x1,y1,x,[],extrapval);
f(5)
I cannot understand why interp1 uses NaN as the default for extrapolation, as 42 has been proven to be the answer to all questions. But if you really want zero to be returned, you can tell interp1 to do that too.
