如何在自定义表达式中引用Spotfire中的轴

Question

This is going to sound ridiculous, but I'm really struggling to follow along with the examples in Spotfire 6.5:

I have a line chart, where I'm trying to produce a cumulative sum of sales. I have dates on the x-axis, correctly identified as DateTime format in Spotfire, and volumes on the y-axis.

I have the custom expression:

Sum([volume]) then Sum([Value]) over (AllPrevious([Axis.X]))

... but I get an error message saying "Could not find axis: 'X'" in the visualization.

Interestingly the UI on the y-axis selector has changed to read "Cumulative Sum (volume)", so I think I must be close... It's just the final hurdle to get over!!

To be completely explicit about this: Should I be using [Axis.X] in my expression, or something like [Date] ?

Answer 1

The data looks like this:

Dates       Sales Cumulative sales

2001-01-09  10    10
2002-01-09  20    30
2003-01-09  30    60
2004-01-09  40    100
2005-01-09  50    150

and the expression for 'Cumulative sales' is: Sum([Sales]) OVER (AllPrevious([Dates]))

Is it what you are looking for ?

Answer 2

Sounds like your X axis isn't categorical, but continuous. In that case the axis won't be available for an OVER expression. Your Y axis expression looks correct.

If you right-click the x axis expression and select "Custom Expression...", the expression for the axis needs to begin with '<' and end with'>'. This means Spotfire will treat values as categories, rather than as measures on a continuous scale. You can also see this by going to X-Axis property page -> Settings button