# Revision history [back]

### plot3d gives me a blank canvas, no plot

This is my function that i want to plot:

v_ges_rhs == -1/((d_e - x)*e_m) + 1/(e_m*x) + 1/(sqrt((d_e - x)^2 + 4*d_k^2)*d_k*(e_m/d_m + e_s/(d_k - d_m))) - 1/(sqrt(4*d_k^2 + x^2)*d_k*(e_m/d_m + e_s/(d_k - d_m)))


and this is my code for inserting values and finally plotting.

print v_ges_rhs
a=v_ges_rhs.diff(x).diff(d_k)
b=a.subs({
d_e : 1,
d_m : .15,
e_m : e_0 * 81,
e_s : e_0 * 3.5
})
b.show()

W = plot3d(b,(x,-1,-0.01),(d_k,.2,2))
W.show()


As you can see, I avoid the poles at x == 0 and x == d_e by not plotting that part. (But actually i would like to plot from x = -1 to 2, including both poles, but limiting the range. I understand that is tricky... I will cross that bridge once I crossed this one.)

But the result I get is an empty canvas.

This is my worksheet. (Feel free to fix any issues you see, preferably with a comment. :-)

https://cocalc.com/share/f7766c5e-2f4d-4916-bb0d-74a7182e5fd5/2019-02-09-203517.sagews?viewer=share