why an extra mark in legend?

*To*: mathgroup at smc.vnet.net*Subject*: [mg106240] why an extra mark in legend?*From*: Haibo Min <haibo.min at gmail.com>*Date*: Wed, 6 Jan 2010 05:57:51 -0500 (EST)

Hello, everyone. Suppose that I have attained a[t], b[t], c[t] in NDSolve. s=NDSolve[...]. Then, I use Plot[{a[t], b[t], c[t]} /. s // Evaluate, {t, 0, 20}, PlotRange -> {{0, 20}, {-2, 1}}, Frame -> True, Axes -> True, FrameLabel -> {"Time(s)", "value"}, PlotStyle -> {{Red, Dashed, Thick}, {Blue, Thick}, {Black, Dotted, Thick}}, PlotLegend -> {"a", "b", "c"}, LegendPosition -> {0.5, -0.3}, LegendSize -> {0.2, 0.3}, LegendShadow -> None] to plot. It was supposed to have three marks in the legend, but I got four, where one of the marks had no text. Why? Thanks. Haibo

**Follow-Ups**:**Re: why an extra mark in legend?***From:*DrMajorBob <btreat1@austin.rr.com>