# Page 117-Mathematica Beyond Mathematics - Par. value in graph label and { }

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 On page 117, in Mathematica Beyond Mathematics it states "You can also include a drop - down button.This will automatically be added when a parameter \ contains five or more choices as shown in the next example.In this \ case we have the possibility to choose several filling alternatives \ for displaying a graph.We use the Plot option : Filling.We also use PlotLabel to show the parameter value when \ labeling the graph.Notice that the combination of Plot options with \ Manipulate greatly increases the number of possible combinations for \ dynamic interactions.Manipulate[ Plot[Sin[nx], {x, 0, 2 [CapitalPi]}, I do not get PlotLabel changing the parameter in labeling the graph. In addition, I receive a list of 2 elements where the second element is the null set.See attachment.Why does the parameter not change in labeling the graph? Also why do I get a list that includes {Null}? Filling [RightArrow] choice, PlotRange [RightArrow] 2, PlotLabel [RightArrow] Style[StringForm["Sin(nt ) representation for n= 1", PaddedForm[n, {4, 2}]], 10]], {n, 1, 20}, {{choice, None, "Choice"}, {None, Axis, Top, Bottom, Automatic, 1, 0.5, 0, -0.5, -1}}, ContentSize [RightArrow] {200, 150}]"However, when I type the following: Manipulate[ Plot[Sin[n x], {x, 0, 2 \[Pi]}, Filling -> choice, PlotRange -> 2, PlotLabel -> Style[StringForm["Sin(n t) representation for n='1'", PaddedForm[n, {4, 2}]], 10]], {n, 1, 20}, {{choice, None, "Choice"}, {None, Axis, Top, Bottom, Automatic, 1, 0.5, 0, -0.5, -1}}, ContentSize -> {200, 150}] , I do not get Attachments:
 I found out the answer to my problem. To be correct you need to replace n='1' by 1. However, I do not understand why I receive {Null} as output. Any suggestions will be very helpful. Attachments: