Re: [Pgfplots-features] Problems when changing axis style for a semilog axis

[Christian F. <lud...@us...>]

Hello Moritz,

sorry for the late answer; I've been busy for some time.

Concerning your questions:
The main point in the provided examples is: log(0) is undefined (or it 
is -infinity). It seems as if pgfplots takes log(ymin) = log(0) = 
undefined and treats it as if you did not provide ymin at all, thereby 
ignoring the value. This shouldn't happen; it should complain instead. 
I'll take a note on my todo list. Nevertheless, it explains why your 
experiments with "/pgfplots/axis x line=bottom,/pgfplots/axis y 
line=left" did not have the desired effect -- pgfplots ignored the 
undefined ymin=0 value and took the value of the data files instead.

Consequently, the "axis x line=middle" which, according to the manual, 
should pass through "y=0", has no effect for logarithmic axes since 
log(y) for y<=0 is undefined. Instead, it has the same effect like axis 
x line=bottom.

Sorry for the improper sanity checking in this case... it will be fixed.


Concerning the "rotate" problem: try adding "transform shape" near 
rotate=-90, it appears to fix the problem according to my tests.
I will try to improve this such that it doesn't need to be provided 
manually.


 > So, is there any way to have a X axis from 0 to 1e6 and a Y axis from
 > 0 to 51 without boxing the plots? Any help is appreciated!

All you did was correct -- except for the ymin=0. You will have to use 
either a linear (non-logarithmic) y axis, or you should resort to some 
strictly positive ymin which is "small enough" like ymin=1e-16 .

Best regards

Christian

Am 13.08.2010 09:22, schrieb nur...@go...:
> Hello,
>
> I'm using pgfplots to draw a figure with four plots using a
> semilogy-axis (code below). Everything works perfectly fine. X- and
> Y-axis cross at (0,0) and form a box.
>
> ---- CODE ----
>
> \begin{tikzpicture}[
>   /pgfplots/width=0.95\textheight,
>   /pgfplots/height=\textwidth,
>   rotate=-90]
> \begin{semilogyaxis}[
>   xlabel={X},
>   ylabel={Y},
>   legend columns=4,
>   xmin=0,
>   xmax=51,
>   ymin=0,
>   ymax=1e6,
>   minor x tick num=4,
>   %/pgfplots/axis x line=middle,
>   %/pgfplots/axis y line=left,
>   legend style= {at={(0.5,0.02)}, anchor=south}
> ]
>
> \addplot[no markers, black!30!white, densely dotted] file {A.dat};
> \addplot[no markers, loosely dashed] file {B.dat};
> \addplot[no markers, black!80!white] file {C.dat};
> \addplot[no markers, densely dashed] file {D.dat};
>
> \legend{A, B, C, D}
> 	
>   \end{semilogyaxis}
> \end{tikzpicture}
>
> ---- CODE END ----
>
> I then added "/pgfplots/axis x line=bottom,/pgfplots/axis y line=left"
> to the options of my "semilogyaxis" to get rid of the box. Now the
> axes cross at (0,1). 1 is indeed yMin when examing the plotted data,
> but not the specified yMin from the axis options. I then tried "axis x
> line=center", but the x-axis is still drawn at 10^0=1, not 0 as stated
> in the manual. Did I misunterstood something?
>
> Another problem occurs when using "axis x line=center" together with
> the "rotate=-90": The figure is moved off to the right side of the
> page, the bottom is visible in the page margin. The label for the
> y-axis is shown in the top left corner of the page... This doesn't
> happen with "bottom" or if I remove the "rotate".
>
> So, is there any way to have a X axis from 0 to 1e6 and a Y axis from
> 0 to 51 without boxing the plots? Any help is appreciated!
>
> Thanks,
>
> Moritz
>
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