# Issue with Plotting sqrt{x-1} Graph Using pgfplots

I'm currently working on a project where I need to plot the graph of the function $\sqrt{x-1}$ using the pgfplots package. However, I've encountered an issue – the graph doesn't seem to pass through the point (1,0).

I've included the necessary \usepackage{pgfplots} in my document preamble, and the graph is displaying, but it's not behaving as expected near the point (1,0). I've double-checked my function expression and the package inclusion, but I'm still facing this problem.

Here's a snippet of my code:

\documentclass{article}
\usepackage{graphicx} % Required for inserting images
\usepackage{booktabs}
\usepackage{tkz-tab}
\usepackage{pgfplots}
\begin{document}
\begin{center}
\begin{tikzpicture}
\begin{axis}[
xlabel={$x$},
ylabel={$y$},
axis lines=middle,
xmin=-2, xmax=6,
ymin=-2, ymax=4,
grid=major,
domain=-2:6,
restrict y to domain=-2:6,
samples=100,
xtick={-2,-1,0,1,2,3,4,5,6},
ytick={-2,-1,0,1,2,3,4,5,6},
]
% Add a node with the text in blue
\node[blue] at (axis cs: 5, 2.5) {$(\mathcal{C}_{f})$};
\end{axis}
\end{tikzpicture}
\end{center}
\end{document}

• Add domain=1:6 to the addplot option. 100 points between -2 and 6 will miss x=1... Jan 10 at 20:52
• And also, have a look at tex.stackexchange.com/questions/375337/… Jan 10 at 20:53
• Finally: look at the warnings and add \pgfplotsset{compat=1.18} to your preamble, after loading pgfplots Jan 10 at 20:54

Other alternatives to pgfplots. The function is simple and doesn't require large tools.

version 1 with tkz-fct

\documentclass{standalone}
\usepackage{tkz-fct}
\begin{document}
\begin{tikzpicture}[gridded]
\tkzInit[xmin=-0,xmax=6,ymin=-1,ymax=4]
\tkzAxeX \tkzAxeY
\tkzFct[domain=1:6,samples=800,draw=blue,thick]{sqrt(x-1)}
\end{tikzpicture}
\end{document}


Version 2 with LuaLaTeX. I loaded tkz-fct only for the axes

% !TEX TS-program = lualatex
\documentclass{article}
\usepackage{tkz-fct}
\begin{document}

\directlua{
function f(t0, t1, n)
local dt = (t1-t0)/n
local t = t0
local out=assert(io.open("tmp.table","w"))
local x,y
while (t <= t1) do
x = t
y = math.sqrt(t-1)
out:write(x, " ", y, " i\string\n")
t = t + dt
end
out:close()
end
}
\begin{tikzpicture}[gridded]
\tkzInit[xmin=-0,xmax=6,ymin=-1,ymax=4]
\tkzAxeX \tkzAxeY
\directlua{f(1,6,100)}
\draw[domain=1:6,thick,blue] plot[smooth] file {tmp.table};
\end{tikzpicture}
\end{document}


\documentclass[12pt]{article}
\usepackage{graphicx} % Required for inserting images
\usepackage{pgfplots}
\begin{document}
\begin{center}
\begin{tikzpicture}
\begin{axis}[
xlabel={$x$},
ylabel={$y$},
axis lines=middle,
axis equal, % Ensure equal scaling on both axes
xmin=0, xmax=6,
ymin=0, ymax=3,
grid=major,
domain=1:6,
restrict y to domain=0:3,
samples=500,
xtick={0,1,2,3,4,5,6}, % Include 0 in xticks
ytick={0,1,2,3},
]
\node[blue] at (axis cs: 5, 2.5) {$(\mathcal{C}_{f})$};