# How to show the directions (arrows in the graph) for a ParametricPlot [duplicate]

f[t_] := 2*t - 3;
f1[t_] := 6*t - 7;
ParametricPlot[{f[t], f1[t]}, {t, -3, 3}]


The above code shows the graph... but it can't show me the directions. How can this be achieved?

## marked as duplicate by J. M. is away♦Dec 14 '15 at 11:05

• Welcome to Mathematica.SE! 1) As you receive help, try to give it too, by answering questions in your area of expertise. 2) Take the tour and check the faqs! 3) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign! – user9660 Dec 14 '15 at 8:58
• – user9660 Dec 14 '15 at 8:58

One way to post-process your plot (caveat: will probably not work for any combination):

f[t_] := 2*t - 3; f1[t_] := 6*t - 7;
ParametricPlot[{f[t], f1[t]}, {t, -3, 3}] /.  Line[content___] :> {Arrowheads[ConstantArray[0.05, 5]], Arrow[content]}


• Thnx....to you. – Nasim Dec 14 '15 at 9:14

This question may get marked as a duplicate, there are many question about adding arrows to plots, but none of them has an answer of how to programmatically add an arrow for a parametric plot. For that answer, I looked to this post on Wolfram Community,

arrowParametricPlot[f_List, p_List, opts : OptionsPattern[]] :=
Block[{δ = (p[[3]] - p[[2]])/100.},
ParametricPlot[f, p,
Evaluate[FilterRules[{opts}, Options[ParametricPlot]]],
Arrow[{f /. p[[1]] -> p[[3]] - δ,
f /. p[[1]] -> p[[3]]}]}, PlotRange -> All]] /;
Length[f] == 2 &&
Length[p] == 3 && ! FreeQ[f[[1]], p[[1]]] && !
FreeQ[f[[2]], p[[1]]]


See that it will show the direction of the parametric curve,

{arrowParametricPlot[{f[t], f1[t]}, {t, -3, 3}, ImageSize -> 100],
arrowParametricPlot[{f[t], f1[t]}, {t, 3, -3}, ImageSize -> 100]}