[vz-dev] line charts are wrong display style for "power" type data!

Harald Koenig H.Koenig at science-computing.de
Tue Jun 28 14:00:29 CEST 2011


one more bug report I'd like to ask/discuss here (so, what's that horrible mantis thing good for anyway;) :


for "power" style data you must not draw lines between measurement points as this gives totally wrong graphs (esp. for pulse counters!).

note: the area/integral below the "power curve" is the electric energy/work which is the key value of the game. right now, the area below the pulse meter graph is *very* wrong!

look at the attached graphs s1..s4 for illustration (see URL above): this is an LCD monitor which got switched on for only short times, brown: current clamp and blue: pulse meter (scaled by a factor of 2 because of flukso not handling 2000 imps/sec correctly at that time).

s1 and s3 show line graphs, s2 and s4 the same interval with dots.
s2/s4 is zoomed into the middle peak around 18:00.

so: for every measurement point you should draw some line or rectangle with the area beyond that line/rect being propotional to the energy in that time interval (== power_value * delta_time). thus with inceasing delta_time, the line should get lower and lower to keep the area the same (== last meter value).

other possibility (which likely is less obvious and visible but valid too):
draw at position "time" a rectangle with height "power_value" but the horizontal with of that rectangle must be scaled (shrinked) so that the area of that rectangle corresponds to the last enerygy quantum (that rectangle must not start at time stamp "n-1"). this might give small/tall needle peak rectangles or even overlapping rectangles, so likely this view is even more disturbing;)

comments ?

Harald Koenig
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