Wsrtjtyk

I use pfgplots to draw two sets of data, stored in .dat. Now I would like to automatically draw an arrow from one curve to the other, and only at the curves points. I tried to name the paths, but to no avail... Here is my minimum working example:

documentclass[11pt]{standalone}

usepackage{tikz,pgfplots,filecontents}

pgfplotsset{compat=newest}

usepgfplotslibrary{fillbetween}

begin{filecontents*}{data1.dat}

a b

1 1

2 1.2

3 1.5

end{filecontents*}

begin{filecontents*}{data2.dat}

a b

1 1.5

2 1.75

3 1.6

end{filecontents*}



begin{document}

    begin{tikzpicture}

        %graphique      

        begin{axis}  

            addplot[name path=c1,blue,thick,mark=*] plot table[x=a,y=b]{data1.dat};

            addplot[name path=c2,black,thick,mark=*] plot table[x=a,y=b]{data2.dat};

            %draw[red,->] (c1) -- (c2);



        end{axis}          

    end{tikzpicture}



end{document}

Which gives:

I would like to get (automatically from data points):

To generate this last picture I defined each arrow separately, for example for the last arrow:
draw[red,-latex,thick,shorten >=0.1em] (3,1.5) -- (3,1.6);

I tryed to use the fillbetween package to name the paths, but I have not been able to use it so far. Could I get something like : draw[red,->] (c1) -- (c2); ?

Thanks a lot for your help!

Here is an alternative based on this nice answer. Its advantage is that it does not rely on the plot points having always the same distance. In fact, in your data set they don't, and that's the reason why in your answer the middle arrow is not vertical. (EDIT: Added your way to determine the number of rows N and adjusted the inner sep of the nodes.)

documentclass[11pt]{standalone}

usepackage{tikz,pgfplots,filecontents}

pgfplotsset{compat=newest}

usepgfplotslibrary{fillbetween}

begin{filecontents*}{data1.dat}

a b

1 1

2 1.2

3 1.5

end{filecontents*}

begin{filecontents*}{data2.dat}

a b

1 1.5

2 1.75

3 1.6

end{filecontents*}



pgfplotsset{

    name nodes near coords/.style={

        every node near coord/.append style={

            name=#1-coordindex,

            alias=#1-last,

        },

    },

    name nodes near coords/.default=coordnode

}



begin{document}

%reads data

pgfplotstableread{data1.dat}{dataA} %beware that "data1" would trigger an error => do not use numbers

pgfplotstablegetrowsof{dataA}

pgfmathtruncatemacro{N}{pgfplotsretval-1} %get access to the number of points in data



begin{tikzpicture}



begin{axis}[

    nodes near coords={},nodes near coords style={anchor=center,inner sep=0pt}

    ]

addplot[blue,thick,mark=*,   name nodes near coords=c] 

table[x=a,y=b]{data1.dat};

addplot+[black,thick,mark=*,   name nodes near coords=d] table[x=a,y=b]{data2.dat};

end{axis}

foreach X in {0,...,N}

{draw[red,-latex] (c-X) -- (d-X);}

end{tikzpicture}

end{document}

Thanks to this previous post, I came up with this solution.

documentclass[11pt]{standalone}

usepackage{tikz,pgfplots}

pgfplotsset{compat=newest}



begin{filecontents*}{data1.dat}

a b

1 1

2 1.2

3 1.5

end{filecontents*}

begin{filecontents*}{data2.dat}

a b

1 1.5

2 1.75

3 1.6

end{filecontents*}



%reads data

pgfplotstableread{data1.dat}{dataA} %beware that "data1" would trigger an error => do not use numbers

pgfplotstablegetrowsof{dataA}

pgfmathtruncatemacro{N}{pgfplotsretval-1} %get access to the number of points in data



begin{document}

    begin{tikzpicture}

        %graphique      

        begin{axis}  

            addplot[blue,thick,mark=*] plot table[x=a,y=b]{data1.dat} 

                foreach i in {0,...,N} {coordinate [pos=i/N] (ai)};

            addplot[black,thick,mark=*] plot table[x=a,y=b]{data2.dat}

                foreach i in {0,...,N} {coordinate [pos=i/N] (bi)};

        end{axis}  

        foreach i in {0,...,N} {

            draw[red,-latex,thick,shorten >=0.1em] (ai) -- (bi);

        }       

    end{tikzpicture}



end{document}

Which gives:

However you'll notice a slight shift of my middle arrow. I think this comes from my data not being evenly distributed... Would you have any insight on this ?