Your function would return all non-real results which can't be plotted, like
You type a square bracket and this creates a matrix - guess this was not your intention.
Maybe you meant it to be the absolute value? Then of course you also would get real results.
But because f is a vector, you will also use vectorization as otherwise only the absolute value of the vector would be the only single scalar value.
Vectorization is also what you need in your second plot
P10 file attached
