Btukfyl

I have the following Tikz picture:

   begin{center}

      begin{tikzpicture}[>=stealth,sloped]

        matrix (tree) [%

          matrix of nodes,

          minimum size=1cm,

          column sep=2.5cm,

          row sep=1cm,

        ]

        {

            $v_1$ &        & $v_3$ & $f_2$ & $v_5$ \

                  &  $f_1$ &       &       &       \

            $v_2$ &        & $v_4$ &       &       \

        };

        draw[->] (tree-1-1) -- (tree-2-2) node [near end,above, rounded corners] {$1$};

        draw[->] (tree-3-1) -- (tree-2-2) node [near end,below] {$2$};

        draw[->] (tree-2-2) -- (tree-1-3) node [near start,above] {$1$};

        draw[->] (tree-2-2) -- (tree-3-3) node [near start,below] {$2$};

        draw[->] (tree-1-3) -- (tree-1-4) node [near end,above] {$1$};

        draw[->] (tree-1-4) -- (tree-1-5) node [near start,above] {$1$};

      end{tikzpicture}

    end{center}

Is it possible to get boxes around the $v_i$ and $f_j$? For instance circles?
I would like to have different boxes for the $v_i$ and $f_j$, because they have a different meaning.

I'm new to Tikz btw.

Kind regards,
Jens

If you want to have the same "box" for all nodes

You can add option nodes={draw,circle} if you want all nodes to be in circle "box":

documentclass[tikz]{standalone}

usetikzlibrary{matrix}

begin{document}

    begin{tikzpicture}[>=stealth,sloped]

        matrix (tree) [%

          matrix of nodes,

          minimum size=1cm,

          column sep=2.5cm,

          row sep=1cm,

          nodes={draw,circle}

        ]

        {

            $v_1$ &        & $v_3$ & $f_2$ & $v_5$\

                   &  $f_1$ &       &       &      \

            $v_2$  &        & $v_4$ &       &      \

        };

        draw[->] (tree-1-1) -- (tree-2-2) node [near end,above, rounded corners] {$1$};

        draw[->] (tree-3-1) -- (tree-2-2) node [near end,below] {$2$};

        draw[->] (tree-2-2) -- (tree-1-3) node [near start,above] {$1$};

        draw[->] (tree-2-2) -- (tree-3-3) node [near start,below] {$2$};

        draw[->] (tree-1-3) -- (tree-1-4) node [near end,above] {$1$};

        draw[->] (tree-1-4) -- (tree-1-5) node [near start,above] {$1$};

    end{tikzpicture}

end{document}

All credits go to Kpym, and this nice proposal is shown in this answer by the author's request.

If you want different styles for different types of nodes

using matrix is still ok, but it is more complicated. I propose a normal solution:

documentclass[tikz]{standalone}

begin{document}

    begin{tikzpicture}[>=stealth,sloped]

        begin{scope}[every node/.style={minimum size=1cm,draw,circle}]

            node (v1) at (0,0) {$v_1$};

            node (v2) at (0,-2) {$v_2$};

            node (v3) at (5,0) {$v_3$};

            node (v4) at (5,-2) {$v_4$};

            node (v5) at (10,0) {$v_5$};

        end{scope}

        begin{scope}[every node/.style={minimum size=1cm,draw,rectangle}]

            node (f1) at (2.5,-1) {$f_1$};

            node (f2) at (7.5,0) {$f_2$};

        end{scope}

        draw[->] (v1) -- (f1) node [near end,above, rounded corners] {$1$};

        draw[->] (v2) -- (f1) node [near end,below] {$2$};

        draw[->] (f1) -- (v3) node [near start,above] {$1$};

        draw[->] (f1) -- (v4) node [near start,below] {$2$};

        draw[->] (v3) -- (f2) node [near end,above] {$1$};

        draw[->] (f2) -- (v5) node [near start,above] {$1$};

    end{tikzpicture}

end{document}