Mizer arrays record what kind of quantity their values are in their type
attribute, because some kinds need handling that the numbers alone do not
reveal:
"value"the default: a rate, an amount, anything that needs no special handling.
"density"an amount per gram of body weight, like a number density. Plotting a density against a length axis restates it per centimetre, which changes the values and not just the axis.
"proportion"a fraction, like the feeding level. Plotted on a linear y axis showing the whole of the interval from 0 to 1, so that the value can be read against the scale it belongs to.