# Why empty plot (Dsolve solution)?

When I try to plot the DSolve output, I get empty plot.

Here is the code

Eq1 = -(r + k)/k*(1 + 1/beta)*D[(D[u[r], r] - (u[r] + 1)/(r + k)), r] == p
bcs1 =  u[-1] == 1;
bcs2 = u[1] == 1;
sol = DSolve[{Eq1, bcs1, bcs2}, u[r], r]
k = 0.1; beta = 0.1; p = 0.1;
Plot[u[r] /. sol, {r, -1, 1}]


I have no idea where, I made a mistake.

Thanks

• When something won't plot, it's useful to look at the numerical values. ThingThatWontPlot/.variable->SomeSensibleValue//N – John Doty Jun 9 '15 at 16:20

One way to see the problem, is to evaluate the solution, using Table for some values:
 Chop@Table[u[r] /. sol, {r, -1, 1, .1}]

So the solution is complex valued. So to plot it, use Re and Im
 Plot[Re[u[r] /. sol], {r, -1, 1}]

 Plot[Im[u[r] /. sol], {r, -1, 1}]