# How to draw a monthly gantt chart with quarterly vgrid?

I recently updated my pgfgantt package, and can't figure out how to update one of my charts to draw properly under the new package. The chart has a two-tiered title, years over months. It also had a quarterly vertical grid. It's the quarterly vertical grid I'm having issues recreating.

My old working code was

\begin{tikzpicture}[x=.5cm, y=1cm]
\begin{ganttchart}%
[today=5.5, vgrid, vgrid lines list={4,7,...,\value{gtt@width}}]{19}
\gantttitle{2012}{12} \gantttitle{2013}{7} \\
\gantttitlelist{1,...,12}{1}\gantttitlelist{1,...,7}{1} \\
\ganttgroup{Prospectus}{1}{7} \\
%% more gantt items omitted
\end{ganttchart}
\end{tikzpicture}


Following the examples in the package documentation I can create a dotted vertical grid for every other month, but not for every third month.

every other month:

\begin{tikzpicture}[x=.5cm, y=1cm]
\begin{ganttchart}%
[today=5.5, vgrid={draw=none, dotted}]{19}
\gantttitle{2012}{12} \gantttitle{2013}{7} \\
\gantttitlelist{1,...,12}{1}\gantttitlelist{1,...,7}{1} \\
\ganttgroup{Prospectus}{1}{7} \\
\end{ganttchart}
\end{tikzpicture}


but vgrid={draw=none, none, dotted} gives the error

ERROR: Package pgfkeys Error: I do not know the key '/tikz/none' and I am going to ignore it. Perhaps you misspelled it.

and vgrid={draw=*2{none}, dotted} gives the error

ERROR: Package xcolor Error: Undefined color *2{none}'.

How can I get two skips followed by a dotted line?

• What version are you running? Am I right in thinking that v3.0 is the most recent? – oLas May 6 '13 at 21:38

The problem is with your syntax for the vgrid style list.
From PGF Gantt Documentation: A style list item has the general syntax *{<n>}{<style>}. You are correct in using the additional draw = none for no style on the vgrid but it should be contained within the style argument {<style>}.
So rather than vgrid={draw=*2{none}, dotted}
You should use vgrid={*2{draw=none}, dotted} This would produce the following output:
• Sounds like an update to the package documentation is in order, because I lifted the vgrid={draw=none, dotted} directly from the doc, but it now appears that this is only half right. In fact, I'm not even sure why it works! Thanks. – mac May 7 '13 at 14:59
• @mac {draw=none, dotted} would work, just not {draw=none, none, dotted} you should use {draw=none, draw=none, dotted}. Hope that helps – oLas May 7 '13 at 16:33
• With vgrid={*2{draw=none}, dotted} you get problems, if you replace 2 with two digit values. So you better use vgrid={*{12}{draw=none}, dotted}`. – knut Mar 3 '18 at 21:01