This is an example of the “tooltips” error in Companion plotting of power history. On the left, power is noted as 159w. On the right, the notation is for 8 seconds later and says 165w, but the plotted line has obviously dropped. So did the power go up or down during those 8 seconds?

A line on a screen as small as a phone, for a dataset as large as power across the time of a ride, will only be an approximation of what’s actually there. I see this notably on Strava’s power graph on the mobile app, where it will say my max power was 50 watts or so above what the graph’s peak shows. So I would assume that this is a similar case; in order to fit a graph onto the screen, the power must be “smoothed” (ie you can’t graphically show every single point, instead finding a line/graph that approximates your power to a reasonable degree). What you get is pretty close to your actually power, but not perfectly.

It does look like the spot in the circle has a brief point where it goes horizontal. So that could be a sign that the power went up before going back down.

I see what you’re saying about not being able to show every point from the ride on the plot, and that’s certainly true. But I would expect that the vertical position of the white circle drawn on the white line would indicate the power level at the chosen point in time (or the average of the previous 1 second, at least). In this case the circle moved downward a little from 38:54 ET to 39:02 ET, but the notation says the power went up 6w. This means that, at best, the code that does the notation and the code that draws the circles are using two slightly different sets of data.

My guess would be that the line is based on actual power and the number displayed is 3 second smoothed power.

so the second one is slightly lower at that exact point but the average overall is higher.

over simplified example:

power one is an average of 100, 120, 115

power two is an average of 120, 115, 110

line would go down from 115 to 110 but the average of the 3 goes from 112 to 115.

Is 3-second data smoothing something that’s been known to be used in Companion?

I don’t know, hence i said “My Guess”.

It is used in game so could be.