Cfrgtkky

The arrays xcoordinates and ycoordinates define points on a grid. I'm simply trying to connect all of the points sequentially with short line segments.

documentclass[12pt]{article}

usepackage{tikz}

usepackage[active,tightpage]{preview}%

PreviewEnvironment{tikzpicture}%

setlengthPreviewBorder{0.1cm}%



usetikzlibrary{positioning}%

usetikzlibrary{shapes}%

usetikzlibrary{arrows}%

usetikzlibrary{calc}%



begin{document}



defthexslant{-1}

deftheyslant{0.5}



newlengthmarkeroffset

setlengthmarkeroffset{0.20cm}



% particle diameter

defmarkerdiameter{0.2cm}





begin{tikzpicture}[scale=.9,every node/.style={minimum size=1cm},on grid]



begin{scope}[

yshift=0cm,every node/.append style={

yslant=theyslant,xslant=thexslant},yslant=theyslant,xslant=thexslant]

fill[white,fill opacity=.9] (0,0) rectangle (5,5);

draw[black,very thick] (0,0) rectangle (5,5);

draw[step=10mm, black] (0,0) grid (5,5);



foreach i / j in {1/1, 1/2, 1/3, 1/4, 1/5, 2/5, 3/5, 3/4, 3/3, 3/2, 3/1, 4/1, 5/1, 5/2, 5/3, 5/4, 5/5}{%

        fill[black] (i - 0.5, j - 0.5) circle (markerdiameter/2);%

        node at (i - 0.5, j - 0.5) [blue,xshift=markeroffset, yshift=markeroffset,font=tiny] () {$i,j$};

}%



% draw a red line indicating the path of the survey



defxcoordinates{{1,1,1,1,1,2,3,3,3,3,3,4,5,5,5,5,5}}

defycoordinates{{1,2,3,4,5,5,5,4,3,2,1,1,1,2,3,4,5}}



% ****** uncomment this to reveal problem

%foreach i in {1,...,15}{

%coordinate (A) at (pgfmathparse{xcoordinates[i]} pgfmathresult, pgfmathparse{ycoordinates[i]} pgfmathresult)-(0.5,0.5);

%coordinate (B) at (pgfmathparse{xcoordinates[i+1]} pgfmathresult, pgfmathparse{ycoordinates[i+1]} pgfmathresult)-(0.5,0.5);

%draw[gray] (B) -- (3,3);

%}



end{scope}



end{tikzpicture}



end{document}

I'm not confident that one can do xcoordinates[i+1]. When I compile this, I get the error:

! Incomplete iffalse; all text was ignored after line 83.

The same mwe with more functionality looks like:

documentclass[12pt]{article}

usepackage{tikz}

usepackage[active,tightpage]{preview}%

PreviewEnvironment{tikzpicture}%

setlengthPreviewBorder{0.1cm}%



usetikzlibrary{positioning}%

usetikzlibrary{shapes}%

usetikzlibrary{arrows}%

usetikzlibrary{calc}%



begin{document}



defthexslant{-1}

deftheyslant{0.5}



newlengthmarkeroffset

setlengthmarkeroffset{0.20cm}



% particle diameter

defmarkerdiameter{0.2cm}





begin{tikzpicture}[scale=.9,every node/.style={minimum size=1cm},on grid]



begin{scope}[

yshift=0cm,every node/.append style={

yslant=theyslant,xslant=thexslant},yslant=theyslant,xslant=thexslant]

fill[white,fill opacity=.9] (0,0) rectangle (5,5);

draw[black,very thick] (0,0) rectangle (5,5);

draw[step=10mm, black] (0,0) grid (5,5);



foreach i / j in {1/1, 1/2, 1/3, 1/4, 1/5, 2/5, 3/5, 3/4, 3/3, 3/2, 3/1, 4/1, 5/1, 5/2, 5/3, 5/4, 5/5}{%

        fill[black] (i - 0.5, j - 0.5) circle (markerdiameter/2);%

        node at (i - 0.5, j - 0.5) [blue,xshift=markeroffset, yshift=markeroffset,font=tiny] () {$i,j$};

}%



% draw a red line indicating the path of the survey



defxcoordinates{{1,1,1,1,1,2,3,3,3,3,3,4,5,5,5,5,5}}

defycoordinates{{1,2,3,4,5,5,5,4,3,2,1,1,1,2,3,4,5}}



% suggestion by marmot

draw[red, very thick] plot[variable=x,samples at={0,...,16}] ({xcoordinates[x]-0.5},{ycoordinates[x]-0.5});



% from the first point to every other point

coordinate (A) at (0.5,0.5);

foreach position in {(1,2), (1,3), (1,4), (1,5), (2,5), (3,5), (3,4), (3,3), (3,2), (3,1), (4,1), (5,1), (5,2), (5,3), (5,4), (5,5)}{

draw[gray] position+(-0.5,-0.5) -- (A);

}%



% and here is how we draw all the possible connections

foreach xa / ya [count=i] in {1/1, 1/2, 1/3, 1/4, 1/5, 2/5, 3/5, 3/4, 3/3, 3/2, 3/1, 4/1, 5/1, 5/2, 5/3, 5/4, 5/5}

foreach xb / yb  [count=j] in {1/1, 1/2, 1/3, 1/4, 1/5, 2/5, 3/5, 3/4, 3/3, 3/2, 3/1, 4/1, 5/1, 5/2, 5/3, 5/4, 5/5}

{

ifnum i=j 

else

draw[gray] (xa-0.5,ya-0.5) -- (xb-0.5,yb-0.5);

fi 

}%



end{scope}



end{tikzpicture}



end{document}

This is really quite ugly (done quickly, learning on the fly) because I'm defining the survey points / coordinates in three different ways. They should only be defined once.

Any suggestions on structure are appreciated.

You do not need any of the pgfmathparse thingies for that. (And you cannot subtract coordinates in the way you seem to intend.)

documentclass[tikz,border=3.14mm]{standalone}

begin{document}

begin{tikzpicture}

defxcoordinates{{1,1,1,1,1,2,3,3,3,3,3,4,5,5,5,5,5}}

defycoordinates{{1,2,3,4,5,5,5,4,3,2,1,1,1,2,3,4,5}}



foreach i [evaluate=i as j using {int(i+1)}] in {1,...,15} {

draw[gray] ({xcoordinates[i]-0.5},{ycoordinates[i]-0.5}) -- ({xcoordinates[j]-0.5},{ycoordinates[j]-0.5});

}

end{tikzpicture}

end{document}

If you really insist on retaining your original syntax to a large extent, you could use calc. And then I would like to argue that, if you create named coordinates, making them unique may help.

documentclass[tikz,border=3.14mm]{standalone}

usetikzlibrary{calc}

begin{document}

begin{tikzpicture}

defxcoordinates{{1,1,1,1,1,2,3,3,3,3,3,4,5,5,5,5,5}}

defycoordinates{{1,2,3,4,5,5,5,4,3,2,1,1,1,2,3,4,5}}



foreach i in {1,...,15} {

coordinate (A-i) at ($({xcoordinates[i]},{ycoordinates[i]} )-(0.5,0.5)$);

coordinate (B-i) at ($({xcoordinates[i+1]} ,{ycoordinates[i+1]})-(0.5,0.5)$);

draw[gray] (A-i) -- (B-i);

}

end{tikzpicture}

end{document}

Of course, you can get (almost) the same result much simpler (still using your lists).

documentclass[tikz,border=3.14mm]{standalone}

begin{document}

begin{tikzpicture}

defxcoordinates{{1,1,1,1,1,2,3,3,3,3,3,4,5,5,5,5,5}}

defycoordinates{{1,2,3,4,5,5,5,4,3,2,1,1,1,2,3,4,5}}



draw[gray] plot[variable=x,samples at={1,...,16}] ({xcoordinates[x]-0.5},{ycoordinates[x]-0.5});

end{tikzpicture}

end{document}

Apart from being shorter, this variant has the advantage that the line joins look good.