[Tex/LaTex] How to make sigmoid function at Tikz

Question

I'm trying to make something like this at Tikz:

The function is:
y=1/(1+e^(-x))

but I don't know how to do it because the axis are at different scales.
Can you help me with it?

Thank you!

P.S. I'd like to add the axis with the numbers and help grids (if it's possible).

Source of the graph

Answer 1

Here's an example of your function using the pgfplots package:

\documentclass{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[
        title = {sigmoid function},
        axis on top = true,
        axis x line = bottom,
        axis y line = left,
        grid = major,
        xlabel = $Z$
    ]
        \addplot[
            blue,
            domain = -5:5,
            samples = 100
        ]
            {1/(1+exp(-x))};
    \end{axis}
\end{tikzpicture}
\end{document}

The axis settings (range, grid, appearance, ..) can be defined in the optional argument of the axis environment. Inside the axis environment you can plot multiple curves or data point series using \addplot macros.

Edit

Here's a version using pgfplots which looks more similar to your example:

\documentclass{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[
        height = 7.3cm,
        width = 11cm,
        title = {sigmoid function},
        axis on top = true,
        axis x line = bottom,
        axis y line = left,
        x axis line style = -,
        y axis line style = -,
        tick align = outside,
        every tick/.append style = {
            black,
            thin
        },
%       grid = major,
        ymin = 0,
        ymax = 1,
        xlabel = $Z$
    ]
        \addplot[
            blue,
            domain = -5:5,
            samples = 100
        ]
            {1/(1+exp(-x))};
    \end{axis}
\end{tikzpicture}
\end{document}