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I am trying to predefine the functions I want to plot. A minimal example of what I am trying to achieve looks like this:

fToPlot = {x, 2 x};
legendToPlot = {"x", "2x"};
Plot[fToPlot, {x, 0, 5}, PlotLegends -> legendToPlot]

To my suprise this produces the following output:

enter image description here

which omits the second entry of the legendToPlot list completely. Why does this happen and how do I fix it?

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1 Answer 1

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Plot interprets fToPlot as a single item rather than a list. Thus you must Evaluate it:

fToPlot = {x, 2 x};
legendToPlot = {"x", "2x"};
Plot[Evaluate@fToPlot, 
     {x, 0, 5}, 
     PlotLegends -> legendToPlot]

Note that:

fToPlot = {x, 2 x};
Plot[Evaluate@fToPlot, 
    {x, 0, 5}, 
    PlotLegends -> "Expressions"]

also works.

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  • $\begingroup$ The option Evaluated ->True can also be used here, I think. $\endgroup$ May 9, 2016 at 23:55
  • $\begingroup$ @J.M. Nope. Doesn't work. Didn't you try it? $\endgroup$ May 9, 2016 at 23:59
  • $\begingroup$ Interesting, what version are you using? Plot[fToPlot, {x, 0, 5}, Evaluated -> True, PlotLegends -> legendToPlot]works on 10.4.1 here. EDIT: Huh, the legends get messed up. This sure looks like a bug... $\endgroup$ May 10, 2016 at 0:04
  • $\begingroup$ 10.4.0.0 on a Mac. I'm not sure your option Evaluated is appropriate here. $\endgroup$ May 10, 2016 at 0:06
  • $\begingroup$ @J.M. - Since at least version 7.0.1, Evaluated is not a documented option for Plot or Graphics from which Plot inherits many of its options. Consequently, none of its behavior can properly be a bug. $\endgroup$
    – Bob Hanlon
    May 10, 2016 at 4:49

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