I want to draw a nodal curve with tikz, that is the curve parametrized by x(t) = t^2 - 1 and y(t) = t^3 - t. To do this, I tried the code
\begin{tikzpicture}
\draw [style = help lines, step = 0.5] (-1, -1) grid (1, 1);
\draw [domain = -1.2:1.2, samples=40, variable=\t] plot ({\t^2 - 1}, {\t^3 - \t});
\end{tikzpicture}
but what I get is
So it seems like the part in the interval -1.2:0 is mirrored, but I don't see what went wrong.
I get the correct picture if I split the interval at 0, and use the lines
\draw [domain = -1.2:0, samples=40, variable=\t] plot ({-1 - \t^2}, {\t^3 - \t});
\draw [domain = 0:1.2, samples=40, variable=\t] plot ({\t^2 - 1}, {\t^3 - \t});
With that I get what I expect, but it fells incredibly hacky:
What did I do wrong here? Or did I run into some bug? Note that I still use Texlive 2017, which is included with Ubuntu 18.04.
\t*\tand\t*\t*\tinstead of\t^2and\t^3. Not only does it work with negative numbers, it is much faster. – John Kormylo Sep 12 '19 at 13:58\t^2is computed usingexp{2*log(\t)). – John Kormylo Sep 12 '19 at 14:01(\t)^2. To me this looks like if\tis substituted by a negative number, the sign is not squared. How is thelogof a negative number computed? – red_trumpet Sep 12 '19 at 14:08