# how can use shade function to color a quarter disc?

I'm trying to draw a quarter disc, I want to use the shade function to make it colorful, but what I get is just a little colorful arc, how can I color a quarter disc

\documentclass[border=30pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usetikzlibrary{arrows.meta, calc, decorations.markings, quotes}
\begin{document}
\begin{tikzpicture}
\textcolor{purple}{
\draw[thick,->] (0,0) -- (2,0) node[anchor=north]{$X_0$};
\draw[thick,->] (0,0) -- (0,2) node[anchor=west]{$Y_0$};}
\draw[pattern=dots](1,0,0) arc (0:90:1);
\draw[thick, red] (0,0) -- ++({1*cos(30)},{1*sin(30)})node[midway, above]{$r$};
\node[above=5pt, left=15pt] at (0,0){$O$};
\end{tikzpicture}
\end{document}

• thank you i solve it, by this command: \fill[pattern=dots, pattern color=red ] (0,0) --(1,0,0) arc (0:90:1)--cycle; – moradov Mar 27 '18 at 10:51

It isn't obvious what you want to do with pattern, given that you say you want to use shading. Either way, the key is to specify a closed path around the area you want to fill.

Here, I leave pattern filling just the edge part and add a shading for the complete quarter disk. You should be able to modify if you desire a different combination.

\documentclass[border=30pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usetikzlibrary{arrows.meta, calc, decorations.markings, quotes}
\begin{document}
\begin{tikzpicture}
\draw[thick,->, purple] (0,0) -- (2,0) node[anchor=north]{$X_0$};
\draw[thick,->, purple] (0,0) -- (0,2) node[anchor=west]{$Y_0$};
\shade [bottom color=blue!50!cyan, top color=magenta, shading angle=-45, opacity=.25] (1,0,0) arc (0:90:1) -- (0,0,0) -- cycle;
\draw[pattern=dots](1,0,0) arc (0:90:1);
\draw[thick, red] (0,0) -- ++({1*cos(30)},{1*sin(30)})node[midway, above]{$r$};
\node[above=5pt, left=15pt] at (0,0){$O$};
\end{tikzpicture}
\end{document}


• @Sebastiano I'm not sure what you mean. Merge the axis with what? You can put the radius r in the background by moving that line before the shading. Is that what you mean for that part? – cfr Mar 27 '18 at 11:07
• @Sebastiano If the OP wants to merge the axes, they can be drawn as a single line. I think that the addition of a black dot at the origin would look a bit odd, since axes don't usually have such a feature. Whether the radius should be slightly shorter depends, I guess, on whether the outer border of the arc is considered part of the quarter or not. You might argue that it should be slightly longer, rather than slightly shorter, I guess. You could also draw the radius first and mark the arc second - then you wouldn't have to worry about adjustments for line width. Is that what you mean? – cfr Mar 27 '18 at 15:34
• I delete my comments- – Sebastiano Mar 27 '18 at 19:26