  Data analysts often need to work with multiple series of
data---conventionally shown as line charts---at once. Few visual
representations allow analysts to view many lines simultaneously without
becoming overwhelming or cluttered. In this paper, we introduce the DenseLines
technique to calculate a discrete density representation of time series.
DenseLines normalizes time series by the arc length to compute accurate
densities. The derived density visualization allows users both to see the
aggregate trends of multiple series and to identify anomalous extrema.
