2
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I want to plot such a figure

enter image description here

I used command Plot[Piecewise[{{1,x<0},{x,x=0},{1,x>0}}],{x,-3,3}].

But it shows wrong results.

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4
  • $\begingroup$ Lookup = vs ==. $\endgroup$
    – Kuba
    Commented Oct 25, 2018 at 11:38
  • $\begingroup$ @Kuba, Okay, but we can not not see the line to point (0,0) $\endgroup$
    – ABCDEMMM
    Commented Oct 25, 2018 at 11:42
  • $\begingroup$ Correct but that was solved by kglr now. Plot is not likely to exactly "hit" x==0 so that is why it looks like a straight line. $\endgroup$
    – Kuba
    Commented Oct 25, 2018 at 11:46
  • $\begingroup$ @Kuba, also, Thanks a lot, Before only do it in PPTX.... .:) $\endgroup$
    – ABCDEMMM
    Commented Oct 25, 2018 at 12:00

2 Answers 2

Reset to default
3
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Update:

ParametricPlot[{ {x, 2}, {0, 2 Rescale[x, {-3, 3}]}}, {x, -3, 3}, 
     AxesLabel -> {Style["x", 16], Style["y", 16]}, 
     AxesStyle -> Arrowheads[0.04], 
     Ticks -> None, ExclusionsStyle -> Automatic, 
     PlotStyle -> Directive[Thick, Black], 
     AspectRatio -> Automatic, PlotRangePadding -> {{.2, .5}, {0., .5}}, 
     ImageSize -> Large ]

enter image description here

Original answer:

ParametricPlot[{{x, 0}, {x, 2}, {0, 2 Rescale[x, {-3, 3}]}}, {x, -3, 3}, 
   Axes -> False, PlotStyle -> Thick]

enter image description here

Alternatively, you can Plot two Piecewise functions with the option ExclusionsStyle:

Plot[{Piecewise[{{0, x < 0}, {2, x > 0}}], 
  Piecewise[{{2, x < 0}, {0, x > 0}}]}, {x, -3, 3}, Axes -> False, 
  ExclusionsStyle -> Automatic, PlotStyle -> Black, AspectRatio -> Automatic]

enter image description here

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7
  • $\begingroup$ where is error in my code? $\endgroup$
    – ABCDEMMM
    Commented Oct 25, 2018 at 11:37
  • $\begingroup$ why we can not see line to (0,0) using my method?? $\endgroup$
    – ABCDEMMM
    Commented Oct 25, 2018 at 11:47
  • $\begingroup$ @ABCDEMMM, (1) you should use x ==0 in the middle piece as Kuba commented (2) even then, it gives a single horizontal line at y==1 with a gap at x==0 . $\endgroup$
    – kglr
    Commented Oct 25, 2018 at 11:51
  • $\begingroup$ how can we add -> x, ->y; symbols?? $\endgroup$
    – ABCDEMMM
    Commented Oct 25, 2018 at 12:26
  • $\begingroup$ @ABCDEMMM, you mean Plot[{Piecewise[{{0, x < 0}, {2, x > 0}}], Piecewise[{{2, x < 0}, {0, x > 0}}]}, {x, -3, 3}, AxesLabel -> {"x", "y"}, AxesStyle -> Arrowheads[0.04], Ticks -> None, ExclusionsStyle -> Automatic, PlotStyle -> Black, AspectRatio -> Automatic, PlotRangePadding -> {{.2, .5}, {0., .5}}]? $\endgroup$
    – kglr
    Commented Oct 25, 2018 at 12:33
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Edit:

Graphics[{Black, AbsoluteThickness@3, Line[{{0, 0}, {0, 3}}], 
  Line[{{-3, 3}, {3, 3}}], AbsoluteThickness[1.5], 
  Arrow[{{-5, 0}, {5, 0}}], Arrow[{{0, 3}, {0, 4}}], 
  Text[Style["x", 16, FontFamily -> "Times New Roman"], {4.5, 0.5}]}]

enter image description here

Here is alternatives:

Show[Plot[UnitStep[x], {x, -3, 3}, 
  PlotStyle -> {Black, AbsoluteThickness@3}, PlotRange -> {0, 1}], 
 Plot[UnitStep[-x], {x, -3, 3}, 
  PlotStyle -> {Black, AbsoluteThickness@3}], 
 AxesStyle -> AbsoluteThickness@3, Ticks -> None, PlotRange -> {0, 1}]

Or

Show[Plot[0, {x, -3, 3}, PlotStyle -> {Black, AbsoluteThickness@3}, 
  PlotRange -> {0, 1}], 
 Plot[1, {x, -3, 3}, PlotStyle -> {Black, AbsoluteThickness@3}], 
 AxesStyle -> AbsoluteThickness@3, Ticks -> None, PlotRange -> {0, 1}]

enter image description here

Or using Graphics

Graphics[{Black, AbsoluteThickness@3, Line[{{0, 0}, {0, 2}}], 
  Line[{{-3, 0}, {3, 0}}], Line[{{-3, 2}, {3, 2}}]}]

enter image description here

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1
  • $\begingroup$ you answer is also very helpful, thank you! $\endgroup$
    – ABCDEMMM
    Commented Oct 25, 2018 at 12:55

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