Flexible line chart x-axis

  maracles Greg_Deckler  Even if this is the expertise of SqlJason and probably have a better solution this is what I came up. 

maracles You are right on needing two charts the one over the other. When you select a single month the days chart will show and if there are multiple ( meaning no filter or more selected than one ) the other visual with show up.

Let's start.

Assumimng you are using a calendar/date table as dimension.

Assuming that the measure you display called [Sales]

Create one  line chart and add months ( I use MonthInCalendar column i.e "Jan 2015" ) in axis..

Create second line chart and add days ( I use Datekey column ) in axis.. ( or copy the first one so you have the same formating & size )

Remove titles.

In the first chart ( months ) add the following measure 

Axis Months =

VAR AllMonths =
CALCULATE (
DISTINCTCOUNT ( 'Calendar'[MonthInCalendar] );
ALLSELECTED ( 'Calendar' )
)

VAR Months =
DISTINCTCOUNT ( 'Calendar'[MonthInCalendar] )

RETURN
IF ( Months <> AllMonths; [Sales] )

Variable Months  always return 1 since the current filter context is one month due to months in axis. 

Variable Allmonths returns the number of months in calendar table ignoring the current filter context months in axis ) BUT not any other filter we select outside the graph..( not preciesly - from more details check ALLSELCTED() http://www.sqlbi.com/articles/understanding-allselected/

Result if we don't select one month in a slicer or other chart our line will be visible...If we select one then the chart shows nothing...Cool

Now in the second chart (days ) add the following 

Axis Days=

VAR AllMonths =
CALCULATE (
DISTINCTCOUNT ( 'Calendar'[MonthInCalendar] );
ALLSELECTED ( 'Calendar' )
)

VAR Months =
DISTINCTCOUNT ( 'Calendar'[MonthInCalendar] )

RETURN
IF ( Months = AllMonths; [Sales] )

The same as the previous but know the line is visible only if we have a month selected in slicer or other chart. (due to the Moths = Allmonths)

Now put one into other so it looks like one. Depending what you select in months one of them will be visible ,mimic the change in axis. 

(red months in axis - green days in axis )

Plus :  You can change color in one graph or other attributes the change in axis is more visible

Minus: when you hoove over with the mouse tooltip only appears for the chart the Z-Score in the front and when this is blank hoovering over blurs the chart.

Hope this can work for you..

P.S. I did enjoy trying to fing the workaround