Two sets of Errorbars

Errorbars are a sore subject for anyone who has tried to make a decent scientific chart in Excel! Here is some more data from the experiment with paper aeroplanes, this time showing the time for the plane to hit the ground, with various different weights attached:

View example as VML

View example as SVG

The fitted line looks plausible, but each time value is actually the average of several readings, and we can use the spread to make a rough estimate of the measurement error. Here is the same chart again with an overlay of a Min-Max plot showing an error band of +/- 0.1 sec.

View example as VML

View example as SVG

Sometimes, you have measurement errors in both the X and Y directions. GraPL uses the Max-min chart twice here, once to plot the vertical error range and once the horizontal. Note that the actual data values are plotted last, so that the marker sits on top of the bars, which looks much tidier.

View example as VML

View example as SVG

This example is constructed with generated data – if anyone has any good data from a real experiment, it would be nice to have a better example here!