Re: avoid spurious vertical segment in step function plot

*To*: mathgroup at smc.vnet.net*Subject*: [mg23338] Re: avoid spurious vertical segment in step function plot*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Thu, 4 May 2000 02:59:08 -0400 (EDT)*References*: <8elmsq$sie@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Murray, Here is two ways based on Split. DeleteVerticals[gr_Graphics, slopeMax_] := gr /. Line[lst_] :> Map[Line, Split[lst, Abs[Divide @@ Reverse[#1 - #2]] < slopeMax &], 1]; For your example: gr = Plot[UnitStep[x], {x, -1, 1}, Frame -> True, PlotRange -> {-.1, 1.1}, Axes -> False] Show[DeleteVerticals[gr, 10]]; gr = Plot[UnitStep[x], {x, -1, 1}, Frame -> True, PlotRange -> {-.1, 1.1}, Axes -> False]; We often need to experiment to avoid cutting out steep sections that we want to retain (thought sometives the dotted forms can be useful) gr = Plot[UnitStep[x], {x, -1, 1}, Frame -> True, PlotRange -> {-.1, 1.1}, Axes -> False] gr2 = Plot[Tan[x], {x, -2Pi, Pi}]; Show[DeleteVerticals[gr2, 100]]; Show[DeleteVerticals[gr2, 30000]]; Here is a version that uses peceived slope. I may be easier to use but it is affected by chabges in the asspect ratio DeleteVerticals2[gr_Graphics, slopeMax_] := gr /. Line[lst_] :> Module[{xmin, xmax, ymin, ymax, ar, scl}, (*get the plot range and the aspect ratio used*) {{{xmin, xmax}, {ymin, ymax}}, ar} = Last /@ AbsoluteOptions[gr, {PlotRange, AspectRatio}]; (* multiplying by scl converts a slope in user coordinates to the \ slope as seen - see note below*) scl = ar (xmax - xmin)/(ymax - ymin); Map[Line, Split[lst, Abs[Divide @@ Reverse[#1 - #2]] scl < slopeMax &], 1]]; Show[DeleteVerticals2[gr2, 200]]; -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Murray Eisenberg" <murray at math.umass.edu> wrote in message news:8elmsq$sie at smc.vnet.net... > Several packages available from MathSource deal with eliminating the > spurious parts of plots of discontinuous functions across vertical > asymptotes. > > Is there some simple way of dealing with the similar problem of > eliminating the spurious vertical line segment in plotting a function > with jumps -- for example, in the following? > > Plot[UnitStep[x], {x, -1, 1}] > > -- > Murray Eisenberg murray at math.umass.edu > Mathematics & Statistics Dept. phone 413 549-1020 (H) > Univ. of Massachusetts 413 545-2859 (W) > Amherst, MA 01003-4515 >