Bdtyktl

I'm relatively new to TikZ and I drew the following graph. However, there is some space around the filled black node. Is there a way to have the lines actually connecting with the node?

EDIT: I'm not sure why it doesn't compile and show the graph in here? Maybe someone could please help me with this?

documentclass{article}

usepackage{tikz}

begin{document}

begin{tikzpicture}[scale=0.8]

node (1) at (0.4, 2.2) [circle,draw] {1};

node (4) at (0.4, 0.6) [circle,draw] {4};

node (3) at (2.6, 0.6) [circle,draw] {3};

node (7) at (1.5,1.5) {};

node (2) at (2.6, 2.2) [circle,draw] {2};



fill (7) circle (2.5pt);



draw[-] (1) to (7);

draw[-] (4) to (7);

draw[-] (3) to (7);

draw[-] (2) to (7);



end{tikzpicture}

end{document}

You can control the space added with the inner sep key:

documentclass{article}

usepackage{tikz}

begin{document}

begin{tikzpicture}[scale=0.8]

node (1) at (0.4, 2.2) [circle,draw] {1};

node (4) at (0.4, 0.6) [circle,draw] {4};

node (3) at (2.6, 0.6) [circle,draw] {3};

node[inner sep=0pt] (7) at (1.5,1.5) {};

node (2) at (2.6, 2.2) [circle,draw] {2};



fill (7) circle (2.5pt);



draw[-] (1) to (7);

draw[-] (4) to (7);

draw[-] (3) to (7);

draw[-] (2) to (7);



end{tikzpicture}

end{document}

You are already using circular node shapes, so why not here? And you can put the filled circle in the middle with barycentric cs: (but since you are naming the ones 1, 2, 3, 4, the syntax is here a bit amusing, which is the main reason why I am posting this ;-). And foreach can make your life easier.

documentclass{article}

usepackage{tikz}

begin{document}

begin{tikzpicture}[scale=0.8]

node (1) at (0.4, 2.2) [circle,draw] {1};

node (4) at (0.4, 0.6) [circle,draw] {4};

node (3) at (2.6, 0.6) [circle,draw] {3};

node (2) at (2.6, 2.2) [circle,draw] {2};

node[inner sep=2.5pt,circle,fill] (7) at (barycentric cs:1=1,2=1,3=1,4=1) {};



foreach X in {1,...,4}

{draw[-] (X) to (7);}



end{tikzpicture}

end{document}

documentclass{article}

usepackage{tikz}

begin{document}

begin{tikzpicture}[scale=0.8]

node (1) at (0.4, 2.2) [circle,draw] {1};

node (4) at (0.4, 0.6) [circle,draw] {4};

node (3) at (2.6, 0.6) [circle,draw] {3};

node (7) at (1.5,1.5) {};

node (2) at (2.6, 2.2) [circle,draw] {2};



node[circle, fill=black, draw=black, minimum size=2.5pt] (7) at (1.5, 1.4) {};



draw[-] (1) to (7);

draw[-] (4) to (7);

draw[-] (3) to (7);

draw[-] (2) to (7);



end{tikzpicture}

end{document}

You forgot begin{document} and you should use a node for the circle as well, where you specify the size and color in the node properties.

using polar coordinates and foreach loop make your code simpler and shorter ...

documentclass[tikz, margin=3.141592mm]{standalone}



begin{document}

    begin{tikzpicture}[scale=0.8,

circ/.style = {circle, draw},

 dot/.style = {circle, fill, inner sep=2.5pt}

                        ]

node (n7) [dot]    {};

foreach i [count=ii] in {135, 45, 315, 225}

node (ii) [circ] at (i:16mm) {ii};

draw (1) -- (3)    (2) -- (4);

end{tikzpicture}

end{document}

I would like to join the celebration by offering an additional solution!

The middle node (7) is defined when drawing the first diagonal (1)--(3).

draw (1) -- (3) node [midway,fill] (7){};

I also factorized the style applied to the nodes with the key every node/.style={circle,draw}

documentclass{article}

usepackage{tikz}

begin{document}

begin{tikzpicture}[scale=0.8,every node/.style={circle,draw}]]

node (1) at (0.4, 2.2) {1};

node (4) at (0.4, 0.6) {4};

node (3) at (2.6, 0.6) {3};

node (2) at (2.6, 2.2) {2};

draw (1) -- (3) node [midway,fill] (7){};

draw (2) to (7)to (4);

end{tikzpicture}

end{document}

You can write draw (1)--(7.center).

documentclass[tikz,border=2mm]{standalone}

begin{document}

begin{tikzpicture}

node (1) at (0.4, 2.2) [circle,draw] {1};

node (4) at (0.4, 0.6) [circle,draw] {4};

node (3) at (2.6, 0.6) [circle,draw] {3};

node (7) at (1.5,1.5) {};

node (2) at (2.6, 2.2) [circle,draw] {2};



fill (7) circle (2.5pt);



draw (1) to (7.center);

draw (4) to (7.center);

draw (3) to (7.center);

draw (2) to (7.center);

end{tikzpicture}

end{document}