TikZ diagrams for economists: A normal pdf with shaded area.

I have been dabbling with the TikZ package to create some diagrams relevant to a first year microeconomics course. The following diagram of the probability density function (pdf) of a normal distribution may be useful to others wishing to integrate similar diagrams into their LaTeX documents or Beamer presentations. To use, insert the following code anywhere you like within a .tex document (you must include \usepackage{tikz} in your header):

The Cumulative Density of Image may be NSFW.
Clik here to view.

Image may be NSFW.
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INSERT INTO .TEX DOCUMENT

\begin{tikzpicture}
% define normal distribution function 'normaltwo'
    \def\normaltwo{\x,{4*1/exp(((\x-3)^2)/2)}}

% input y parameter
    \def\y{4.4}

% this line calculates f(y)
    \def\fy{4*1/exp(((\y-3)^2)/2)}

% Shade orange area underneath curve.
    \fill [fill=orange!60] (2.6,0) -- plot[domain=0:4.4] (\normaltwo) -- ({\y},0) -- cycle;

% Draw and label normal distribution function
    \draw[color=blue,domain=0:6] plot (\normaltwo) node[right] {};

% Add dashed line dropping down from normal.
    \draw[dashed] ({\y},{\fy}) -- ({\y},0) node[below] {$y$};

% Optional: Add axis labels
    \draw (-.2,2.5) node[left] {$f_Y(u)$};
    \draw (3,-.5) node[below] {$u$};

% Optional: Add axes
    \draw[->] (0,0) -- (6.2,0) node[right] {};
    \draw[->] (0,0) -- (0,5) node[above] {};

\end{tikzpicture}

The Probability of Image may be NSFW.
Clik here to view. Falling Between Image may be NSFW.
Clik here to view. and Image may be NSFW.
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Image may be NSFW.
Clik here to view.

INSERT INTO .TEX DOCUMENT

\begin{tikzpicture}
% define normal distribution function 'normaltwo'
    \def\normaltwo{\x,{4*1/exp(((\x-3)^2)/2)}}

% input x and y parameters
    \def\y{4.4}
    \def\x{3.4}

% this line calculates f(y)
    \def\fy{4*1/exp(((\y-3)^2)/2)}
    \def\fx{4*1/exp(((\x-3)^2)/2)}

% Shade orange area underneath curve.
    \fill [fill=orange!60] ({\x},0) -- plot[domain={\x}:{\y}] (\normaltwo) -- ({\y},0) -- cycle;

% Draw and label normal distribution function
    \draw[color=blue,domain=0:6] plot (\normaltwo) node[right] {};

% Add dashed line dropping down from normal.
    \draw[dashed] ({\y},{\fy}) -- ({\y},0) node[below] {$y$};
    \draw[dashed] ({\x},{\fx}) -- ({\x},0) node[below] {$x$};

% Optional: Add axis labels
    \draw (-.2,2.5) node[left] {$f_Y(u)$};
    \draw (3,-.5) node[below] {$u$};

% Optional: Add axes
    \draw[->] (0,0) -- (6.2,0) node[right] {};
    \draw[->] (0,0) -- (0,5) node[above] {};

\end{tikzpicture}

The TikZ code snippet above is meant to be dropped into a .tex document and work without any further “tinkering”. Please let me know if this is not the case!