Last N Weeks displayed on a chart different to result in Card

[joebend]

Hello,

Racking my brain to try and understand what (probably very simple) I am missing here.

I have some data that I am creating a measure for to show the last N number of weeks Sales based upon a parameter. I am using the following DAX and this works when displayed in a card.

However, when I add the measure to a line graph/ bar chart and add the date in the x axis it shows me all dates, not just the last N number that I am looking for.

The chart I would be expecting to see would only contain the dates of the last 4 weeks on the x axis, not all as show below.

LNW Sales = CALCULATE([Switch Sales], DATESINPERIOD(Sales[Date], LASTDATE(Sales[Date]),-(LastN[LastN Value]*7),DAY))

[HotChilli]

I'll have a go at this since no-one else has chipped in.

My first recommendation is to use a date table (with a relation to the fact table) whenever time intelligence functions are called.  A lot of problems are solved by doing this.  So that first bit after DATESINPERIOD should be a date column from a date table.

The next thing is that, if i understand you correctly, you want to get a range which goes up to the last date in the sales table. Either 1, 2, 3 etc weeks back from this date and you want the chart to dynamically adjust to show the range on the x-axis.

However, the LASTDATE function in the current measure will take on a different value for each date value on the x-axis.  You could probably see this quite clearly by showing the data in a table.  I think the measure at the moment produces a kind of rolling sales total(if that's what [switch sales] is)  going back n weeks for any sales date.  It works in a card because there won't be a series of date values.

You need to find a way of telling the measure that LASTDATE should refer to the last sales date.  I'm going to take a bit of a flyer and say that putting ALL() round the Sales Date in the LASTDATE clause will get you this.

And the last part is, how is that LastN picked up from the slicer?  Because there's no SELECTEDVALUE or other function wrapping the call.