
1. Re: How do I get a linear trend line model to show the correct yaxis intercept value?
Jonathan Drummey Feb 22, 2013 10:52 AM (in response to Greg Michalski)Tableau's trendline calculation is internal to Tableau so we don't have visibility into it, I suggest you contact support@tableausoftware.com.

2. Re: How do I get a linear trend line model to show the correct yaxis intercept value?
Greg Michalski Feb 23, 2013 6:11 AM (in response to Greg Michalski)OkI figured this out and this may help others. Apparently Tableau uses the same numerical values for dates that Excel uses. So, when Tableau generates a trendline equation, you have to use the correct number for the date of interest. Originally, I was looking at the yaxis and where the trendline was intercepting it (around .58 in this case) and wondering why (when x = 0 in the standard line equation y=ax+b) "b" did not equal .58. It turns out that if you convert the date of interest (9/1/2002 in this case) to its numerical value (37500), the equation works as expected. All this said, there is probably an easier/better way to do all this, although I've found Tableau to be somewhat "finicky" when it comes to using dates in timeseries/trendline type analyses. Hope this is of use to others. Here is a screenshot summary of all this: