pgfplotsplot
I'd like to create a graph of the sign function in my document:
using pdfplots and tizkpicture (as used here). Could you please let me know how to define the function in the addplot part?
\documentclass{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
xlabel=$x$,
ylabel={$\sgn(x)$}
]
\addplot {?????};
\end{axis}
\end{tikzpicture}
\end{document}
This happens because PGFPlots only uses one "stack" per axis: You're stacking the second confidence interval on top of the first. The easiest way to fix this is probably to use the approach described in "Is there an easy way of using line thickness as error indicator in a plot?": After plotting the first confidence interval, stack the upper bound on top again, using stack dir=minus. That way, the stack will be reset to zero, and you can draw the second confidence interval in the same fashion as the first:
\documentclass{standalone}
\usepackage{pgfplots, tikz}
\usepackage{pgfplotstable}
\pgfplotstableread{
temps y_h y_h__inf y_h__sup y_f y_f__inf y_f__sup
1 0.237340 0.135170 0.339511 0.237653 0.135482 0.339823
2 0.561320 0.422007 0.700633 0.165871 0.026558 0.305184
3 0.694760 0.534205 0.855314 0.074856 -0.085698 0.235411
4 0.728306 0.560179 0.896432 0.003361 -0.164765 0.171487
5 0.711710 0.544944 0.878477 -0.044582 -0.211349 0.122184
6 0.671241 0.511191 0.831291 -0.073347 -0.233397 0.086703
7 0.621177 0.471219 0.771135 -0.088418 -0.238376 0.061540
8 0.569354 0.431826 0.706882 -0.094382 -0.231910 0.043146
9 0.519973 0.396571 0.643376 -0.094619 -0.218022 0.028783
10 0.475121 0.366990 0.583251 -0.091467 -0.199598 0.016664
}{\table}
\begin{document}
\begin{tikzpicture}
\begin{axis}
% y_h confidence interval
\addplot [stack plots=y, fill=none, draw=none, forget plot] table [x=temps, y=y_h__inf] {\table} \closedcycle;
\addplot [stack plots=y, fill=gray!50, opacity=0.4, draw opacity=0, area legend] table [x=temps, y expr=\thisrow{y_h__sup}-\thisrow{y_h__inf}] {\table} \closedcycle;
% subtract the upper bound so our stack is back at zero
\addplot [stack plots=y, stack dir=minus, forget plot, draw=none] table [x=temps, y=y_h__sup] {\table};
% y_f confidence interval
\addplot [stack plots=y, fill=none, draw=none, forget plot] table [x=temps, y=y_f__inf] {\table} \closedcycle;
\addplot [stack plots=y, fill=gray!50, opacity=0.4, draw opacity=0, area legend] table [x=temps, y expr=\thisrow{y_f__sup}-\thisrow{y_f__inf}] {\table} \closedcycle;
% the line plots (y_h and y_f)
\addplot [stack plots=false, very thick,smooth,blue] table [x=temps, y=y_h] {\table};
\addplot [stack plots=false, very thick,smooth,blue] table [x=temps, y=y_f] {\table};
\end{axis}
\end{tikzpicture}
\end{document}
As already explained in some comment, \pgfmathsetmacro{72400} is unsupported by PGF (in fact, my system accepts it without problems - apparently something has changed in PGF CVS).
Nevertheless, you do not need \pgfmathsetmacro just to declare a constant; it is much simpler to write \def\MACRO{<constant>} (or use \newcommand\MACRO{<constant>} which should be the same).
Then you need to assign a domain. The key(s) restrict * to domain are no definition how to sample points; they can be used to exclude already sampled points from the region of interest. In your case, you would define domain=775 and omit the restrict * to domain.
Finally, math expressions in parametric plots need extra curly braces if they contain other round braces. In other words, use ({x/\modulus+0.002*(x/\yield)^15},x) to avoid confusion with the round braces (TeX cannot automatically balance them, it can only balance curly braces).
Taking this together, I arrive at the following modification of your first plot:
\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.10}
\begin{document}
\pgfplotsset{stressstrainset/.style={%
axis lines=center,
xlabel={$\varepsilon$},
ylabel={$\sigma$},
%restrict x to domain=0:15,
domain=0:775,
xmin=0.0, xmax= 15,
ymin=0.0, ymax= 775,
samples=100,
}}
\begin{tikzpicture}
\def\modulus{72400}
\def\yield{325}
\begin{axis}[stressstrainset]
\addplot[black] ({x/\modulus+0.002*(x/\yield)^15},x);
\end{axis}
\end{tikzpicture}
\end{document}
Best Answer
The following example solves the function drawing by dividing it into parts:
The minus sign of y tick "-1" would be overprinted by the red line. Therefore, the tick is set as extra tick with a style that moves the tick mark to the right.