Stepped Line Chart - "step after" interpolation mode

[ali_b]

Currently the line chart "step" line type will change values half way between each data point which tricks the eye into thinking a value changed at a specific point in time, when it didn't.

A "step after" interpolation mode should be implemented so that the value of the first data point is held until the value of the second data point. This issue is discussed in these two community threads:

1) https://community.fabric.microsoft.com/t5/Desktop/discrete-graph-step-chart/td-p/1842169

2) https://community.fabric.microsoft.com/t5/Desktop/Stepped-line-chart-changing-the-course-in-the-midd...

I use line charts to show trends, and compare values between trends. Linear interpolation between points might be helpful in some use cases but comparing between interpolated values is often useless when your data is relatively sparse and especially when your data points are not aligned in time (so you end up comparing a real data point to an interpolated data point).

Most other BI / visualisation tools have a "step after" interpolation mode where the value of a point is held until the next data point.

Work arounds include things like creating date spines (causes issues with knowing which points are reall data points), using line charts (and making the comparisons inacrruate), or using bar charts (making comaprisons between points in time difficult).

[v-yetao1-msft]

Hi @ali_b 

Thanks a lot for your feedback, you mentioned that there is also a corresponding workaround inside the two community threads. i'm wondering, what is the final result you want to achieve?

Best Regards,
Community Support Team _ Ailsa Tao

[ali_b]

Hi - the community threads point at the Microsoft "Power KPI" custom visual as a possible solution. However, this visual doesn't have the same features as the standard line chart, eg: it doesn't have the axis zoom features as reported in this reply (and I've confirmed myself) so I can't use it: 

https://community.fabric.microsoft.com/t5/Desktop/discrete-graph-step-chart/m-p/1850954#M714909

At the moment the standard line chart visual implements a very strange step algorithm where the step is always halway between two data points. For example, if you have 4 data points at the start of 1900, 1902, 1904, and  2004, then the step will occur at 1901, 1903, and ... 1954 ?!  The graph seems to suggest your data changed in 1954 instead of 2004.

This is so strange, that I think the stepped interpolation algorithm for the standard line chart is broken, or the visual should at least offer "step-after" as well as the current step algorithm.

Hope that helps?  (love power BI, hope we can continue to make it better 🙂 )

[StefanLyon]

I also feel this would be an extremely useful feature. There is a need at my firm for a line chart with "step after" behavior as well. Definitely add this!