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想把Proximal_Algorithms.pdf的Figure 1画下来：
初步尝试：
%20--%20(3,0);%0D%0A%20%20%5Cdraw%5B-%3E%5D%20(0,0)%20--%20(0,3);%0D%0A%0D%0A%20%20%5Cdraw%5Bthick,domain=-3:3%5D%20plot%20(%7B%5Cx%7D,%7Babs(%5Cx)%7D);%0D%0A%20%20%5Cdraw%5Bthick,domain=-1:3,gray%5D%20plot%20(%7B%5Cx%7D,%7Babs(%5Cx)+0.5*(%5Cx-1.5)%5E2%7D);%0D%0A%20%20%5Cdraw%5Bdashed,domain=-3:3%5D%20plot%20(%7B%5Cx%7D,%7B%5Cx*%5Cx%2F2%7D);%0D%0A%0D%0A%20%20%5Cfill%5Bblack%5D%20(1.5,1.5)%20rectangle%20++(0.1,0.1);%0D%0A%20%20%5Cfill%5Bblue%5D%20(1.5,1)%20circle%20(2pt);%0D%0A%20%20%5Cdraw%5Bred%5Dplot%5Bmark=x%5D%20(0.5,1);%0D%0A%5Cend%7Btikzpicture%7D)
首先应该绘制 $f(x)=|x|$
绘制黑点 (1.5,1.5)
然后用灰色粗线绘制函数 $\abs x+\frac12(x-1.5)^2$，并标记其最小值点 ( 0.5,1) 用一个红x（见Tikz手冊22.7 Placing Marks on the Plot），然后在 (1.5,1) 处画一个蓝色实心小圆圈，并以虚线绘制函数x^2/2 。
domain限制为 xmin=-3,xmax=3,ymin=0,ymax=3，轴不加标签，刻度线放置在左侧和底部
例如這個圖, 取$h(x)=|x|$, $\lambda=1$的情況
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