MATLAB: Matlab plots the equation wrong

Question

x=-20:0.1:20;
f2=x.^10-1;
plot(x,f2)

I cant understand why it sketches my basic code wrong.

Answer 1

MATLAB has plotted exactly what you asked for, where the y-range ranges over:

>> x = -20:0.1:20;
>> y = x.^10-1;
>> max(y)
ans = 10239999999999
>> min(y)
ans = -1

Over that range of y-values I would not expect to be able to distinguish between 0 and -1, they will appear exactly the same on your monitor (unless you have a monitor with more than eleven trillion pixels vertically, in which case those two values will appear one pixel different from each other).

You can limit the plot's y-range if you want:

ylim([-1,3])

or reduce the x-domain:

x = -1.1:0.1:1.1;