MHB Fixing Picture Placement Below Margin

[Dustinsfl]

This picture is on a blank piece of paper but is rendered 2in below the margin. Why is this happening? I want it to be at the top of page right below the margin.
The $z$ node is causing the problem. If I remove the $z$ node, the picture moves back to the top. What can I do about this?

\begin{center}
\begin{tikzpicture}[scale = 1.25]
\draw (0,0) -- (0,3);
\draw (0,0) -- (2.5,0);
\draw (0,0) -- (-1,-1.7);
\draw (-1.5,0) arc (180:360:1.5cm and .5cm);
\draw[dashed] (-1.5,0) arc (180:0:1.5cm and .5cm);
\draw (-1.5,0) -- (-1.5,2);
\draw (1.5,0) -- (1.5,2);
\draw (-1.5,2) arc (180:360:1.5cm and .5cm);
\draw (-1.5,2) arc (180:0:1.5cm and .5cm);
\draw -- node {$y$} (2.1in,0);
\draw -- node {$z$} (0,2.5in);
\draw -- node {$x$} (-.86in,-1.5in);
\end{tikzpicture}
\end{center}

 

[Dustinsfl]

As you can see there is huge gap from where the 1in margin is to the start of the tikz picture
View attachment 544

 

[Evgeny.Makarov]

\draw (0,0) -- (0,3);
...
\draw -- node {$z$} (0,2.5in);

This is a strange way to write "z". I did not know it is possible to omit the first point in the \draw command. Apparently, the second \draw command above is equivalent to

\path (0,0) -- node {$z$} (0,2.5in);

The command \path without options does not draw anything. "The only effect is that the area occupied by the picture is (possibly) enlarged so that the path fits inside the area. To actually “do” something with the path, an option like draw or fill must be given somewhere on the path" (TikZ 2.10 manual, chapter 14). The command \draw is a contraction for \path[draw].

Next, by default when "node" is specified before the second point, the node is placed midway on the line (section 16.9). So what happens is the picture is enlarged to encompass the point (0,2.5in), but "z" is drawn only at (0,1.25in).

 

[Dustinsfl]

This is a strange way to write "z". I did not know it is possible to omit the first point in the \draw command. Apparently, the second \draw command above is equivalent to

\path (0,0) -- node {$z$} (0,2.5in);

The command \path without options does not draw anything. "The only effect is that the area occupied by the picture is (possibly) enlarged so that the path fits inside the area. To actually “do” something with the path, an option like draw or fill must be given somewhere on the path" (TikZ 2.10 manual, chapter 14). The command \draw is a contraction for \path[draw].

Next, by default when "node" is specified before the second point, the node is placed midway on the line (section 16.9). So what happens is the picture is enlarged to encompass the point (0,2.5in), but "z" is drawn only at (0,1.25in).

I am confused. What is going wrong?

 

[Evgeny.Makarov]

Because of the instruction

\draw -- node {$z$} (0,2.5in);

your picture includes the point (0,2.5in), but "z" is drawn at (0,1.25in). Thus, there is 1.25in of white space above (the center of) "z". You can see this if you add the line

\draw (current bounding box.north west) rectangle (current bounding box.south east);

before "\end{tikzpicture}". You can also replace

\draw -- node {$z$} (0,2.5in);

with

\draw (0,0) -- node {$z$} (0,2.5in);

to see that the top end of the line lies on the top edge of the bounding box and "z" is directly in the middle of that line.

 

[Dustinsfl]

Because of the instruction

\draw -- node {$z$} (0,2.5in);

your picture includes the point (0,2.5in), but "z" is drawn at (0,1.25in). Thus, there is 1.25in of white space above (the center of) "z". You can see this if you add the line

\draw (current bounding box.north west) rectangle (current bounding box.south east);

before "\end{tikzpicture}". You can also replace

\draw -- node {$z$} (0,2.5in);

with

\draw (0,0) -- node {$z$} (0,2.5in);

to see that the top end of the line lies on the top edge of the bounding box and "z" is directly in the middle of that line.

Ok I understand. I had to adjust as such to get z in the correct place though. How else can I specify it?

 

[Evgeny.Makarov]

Ok I understand. I had to adjust as such to get z in the correct place though. How else can I specify it?

Yes, I should have said this earlier. When "node {...}" is placed not between "--" and a point, but after a point, then the node is placed at that point. You can also specify options like [above] after "node". So, you can get the same result, but without the extra space above if you replace

\draw (0,0) -- (0,3);

with

\draw (0,0) -- (0,3) node[above] {$z$};

This is described in sections "Placing nodes on a curve explicitly" and "Placing nodes on a curve implicitly" (or something like that) in the manual.