3

The power functions that i'm trying to plot isn't showing up fully, i've tried changing the domains and stuff but to no avail, can i get some help here please?

\documentclass{article}
\usepackage{amsmath}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
     axis lines = center,
    xlabel = $x$,
    ylabel = {$y$},
    xmax = {4},
    xmin = {-1},
    ymax = {2},
    ymin = {-2},
    legend pos = outer north east
]
\addplot [
    domain=-10:10, 
    samples=100, 
    color=black,
]
{x^(1/2)};
\addlegendentry{$y=\sqrt{x}$}
\addplot [
    domain=-5:5, 
    samples=100, 
    color=blue,
]
{x^(1/4)};
\addlegendentry{$y=x^{\frac{1}{4}}$}
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}
\begin{axis}[
    axis lines = center,
    xlabel = $x$,
    ylabel = {$y$},
    xmax = {4},
    xmin = {-4},
    ymax = {2},
    ymin = {-2},
    legend pos = north west
]
\addplot [
    domain=-10:10, 
    samples=100, 
    color=black,
]
{x^(1/3)};
\addlegendentry{$y=x^{\frac{1}{3}}$}
\addplot [
    domain=-10:10, 
    samples=100, 
    color=blue,
]
{x^(1/5)};
\addlegendentry{$y=x^{\frac{1}{5}}$}
\end{axis}
\end{tikzpicture}
\end{document}
10
  • 1
    Please make it compilable by adding document class and packages required. Welcome. – Jesse Feb 8 '16 at 4:20
  • 1
    Welcome to TeX.SE. As Jesse said, It is always best to compose a fully compilable MWE that illustrates the problem including the \documentclass and the appropriate packages so that those trying to help don't have to recreate it. I would recommend you use (x) instead of just x. Otherwise I get two graphs output. Also, please clarify what you mean by "showing up fully". – Peter Grill Feb 8 '16 at 4:25
  • My apologies, i've edited it accordingly. By not showing up fully, i mean that the graphs of y=x^(1/3) and y=x^(1/5) are not showing up at the 3rd quadrant as it is supposed to. – Tay Yong Qiang Feb 8 '16 at 4:32
  • Try using (x) instead of x and PGF Math Function to compute cube root may be of help. – Peter Grill Feb 8 '16 at 5:12
  • 1
    @cmhughes: Yes it is that simple, but that is assuming one can read the code. I can actually relate to the OPs difficulties as it often takes me several guesses as to where to make slight changes to some of the expl3 solutions I am using. Similarly, when it comes to expansion issues. Also, there was a bizarre issue of the 2nd plot needing a \hspace*{-23.5cm} to be able to see it -- see the edit history. Jake rescued me on that one so no longer an issue. – Peter Grill Feb 8 '16 at 22:01
3

You can adapt the solution from PGF Math Function to compute cube root to generate a function that computes the third and fifth root:

enter image description here

References:

Code:

\documentclass{article}
\usepackage{amsmath}
\usepackage{pgfplots}
\pgfplotsset{compat=1.13}

\pgfmathdeclarefunction{CubeRoot}{1}{%
    \pgfmathparse{ifthenelse(#1<0,-1,1)*exp((ln(abs(#1)))/3)}%
}

\pgfmathdeclarefunction{FifthRoot}{1}{%
    \pgfmathparse{ifthenelse(#1<0,-1,1)*exp((ln(abs(#1)))/5)}%
}


\begin{document}\noindent
\begin{tikzpicture}
\begin{axis}[
     axis lines = center,
    xlabel = $x$,
    ylabel = {$y$},
    xmax = {4},
    xmin = {-1},
    ymax = {2},
    ymin = {-2},
    legend pos = south east
]
\addplot [
    domain=0:4, 
    samples=100, 
    color=orange,
    line width=1.0pt,
]
{(x)^(1/2)};
\addlegendentry{$y=\sqrt{x}$}
\addplot [
    domain=0:5, 
    samples=100, 
    color=blue,
    line width=1.0pt,
]
{(x)^(1/4)};
\addlegendentry{$y=x^{\frac{1}{4}}$}
\end{axis}
\end{tikzpicture}
\par
\noindent
\begin{tikzpicture}
\begin{axis}[
    axis lines = center,
    xlabel = $x$,
    ylabel = {$y$},
    xmax = 4,
    xmin = -4,
    ymax = 2,
    ymin = -2,
    legend pos = south east,
    clip=true,
]
\addplot [
    domain=-4:4, 
    samples=100, 
    color=blue, 
    line width=1.0pt,
]
{CubeRoot(x)};
\addlegendentry{$y=x^{\frac{1}{3}}$}
\addplot [
    domain=-4:4, 
    samples=100, 
    color=red,
    line width=1.0pt,
]
{FifthRoot(x)};
\addlegendentry{$y=x^{\frac{1}{5}}$}
\end{axis}
\end{tikzpicture}
\end{document}
1
  • 1
    @Jake: Thanks. That was quite the space for a missing %. Whatever happened to multiple spaces are treated as a single space? :-) – Peter Grill Feb 8 '16 at 8:38

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