well ... question is not only about line chart, but applies also to a column-chart.

I have created an experimental content-type "body data", with 3 fields. a date filed (YY-MM-DD) , a bodyweight field (decimal) and a bodyfat field (decimal). I would like to display a graph where at every date 2 values are displayed (either as dot of a line or like a column).

so i added nodes of the body-data-type,
date weight body fat
20120901 110 18
20120902 109 17
20120903 108 16
20120904 106 14

then trying to create the necessary view with dataviz

basically i do manage to display either the line-chart for the weight development, or the line-chart for the body-fat development

but I can't get them to display both

if i have both fields in the view to display i am ending upp with a chart displaying
110 for 20120901
17 for 20120902
108 for 20120903
14 for 20120904

what am i missing or what am I doing wrong?