I'm beginning to learn pgfplots and I would like to plot some functions: cubic root, inverse, and some trigonometric functions.
The problem is that for y=1/x function, it joins up the points between negative and positive parts of the domain: we can't see the asymptote.
\documentclass{minimal}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[]
\addplot [domain=-10:10, samples=100]{x^(-1)};
\end{axis}
\end{tikzpicture}
\end{document}
With the function y=x^{1/3}, it doesn't display the negative part of the domain.
And with the trigonometric functions, it just doesn't do anything right…
\addplot[domain=-27:27]{x^(1/3)};
\addplot[domain=-2*pi:2*pi]{cos(rad(x))};
thank you very much if you can help me a little bit.
thank you very much for your answers, it's really helping.
Just a last thing: the cubic root function has a negative part in its domain that cannot be displayed. Do you know why?
\begin{tikzpicture}
\begin{axis}[
width=8cm,xlabel={$x$},
ylabel={$y$},grid=both, axis x line=middle, axis y line=middle,
title={$f(x)=x^{1/3}$}]
\addplot[blue,domain=-27:27, no markers,samples=100] {x^(1/3)};
\end{axis}
\end{tikzpicture}
NB: Yes, the cubic root function has a partially negative domain, and no, there is no imaginary part.
NB: i'm sorry i'm insisting on one of my first questions in this comment which is supposed to be an "answer", i'm just new here and, as i'm not registered yet, i don't know how i can ask something related with the topic in a new "question comment"
Best Answer
To keep the negative and positive parts of the
1/x
plot separate, you need to make sure that the function is evaluated atx=0
. If your domain is symmetric, you can just specify an odd number of samples (samples=101
, for example). You also have to make sure that non-real values aren't just silently discarded, but cause a jump in the plot. To do that, specifyunbounded coords=jump
(instead of the default behaviourdiscard
).The trigonometric functions in PGF expect degrees, so you'll have to convert radians to degrees using
deg(x)
(notrad(x)
, that's used for converting degrees to radians).