How to plot a Root[] object?

Question

I got a solution in the form of a Root object from an equation:

y = Root[-1.1292882469618184`*^35 N^3 + 
    3.327201082265235`*^35 N^2 #1 - 
    3.2676236770106753`*^35 N #1^2 + (1.0697043581639466`*^35 + 
       4.055934940208895`*^29 N^2) #1^3 + 
    8.11186988041779`*^29 N #1^4 + 4.055934940208895`*^29 #1^5 &, 1]

which can be evaluated when I substitute the variable N with some number between 1 and 3:

y /. N -> 1
0.993688

However, I am not able to make Mathematica plot y in the range of [1,3]:

Plot[y, {N, 1, 3}]

The error message is "Limiting value 1 in {N,1,3} is not a machine-sized real number".

So what is the problem here and how can I solve it?

As @UlrichNeumann mentions,N is a preserved keyword in Mathematica, so you'd better not use symbols like N, and C, O, etc., or afterwards things may get weird like this problem. :-) — SnzFor16Min, Jul 01 '20 at 13:37
This answer your question: find where 3 inequalities are simultaneously greater than zero — Artes, Jul 01 '20 at 13:38

score 4 · Accepted Answer · answered Jul 01 '20 at 12:40

Don't use N as a symbolname, because it's a predefined Mathematica function!

Try

y = Root[-1.1292882469618184`*^35 N^3 + 3.327201082265235`*^35 N^2 #1 -3.2676236770106753`*^35 N #1^2 + (1.0697043581639466`*^35 +4.055934940208895`*^29 N^2) #1^3 + 8.11186988041779`*^29 N #1^4 + 4.055934940208895`*^29 #1^5 &, 1] /. N -> n;
Plot[y ,{n,1,3}]

How to plot a Root[] object?

1 Answers1