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Re: Possible bug in Opacity[] with plotting function that uses UnitStep?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105612] Re: Possible bug in Opacity[] with plotting function that uses UnitStep?
  • From: dh <dh at metrohm.com>
  • Date: Fri, 11 Dec 2009 04:18:25 -0500 (EST)
  • References: <hfqgmj$ol0$1@smc.vnet.net>


Hi Nasser,

my interpretation:

If you give two items in: FillingStyle -> {Blue, Opacity[0.5]} this is 

interpreted as: fill negative values with Blue and positive values with 

Opacity[0.5] and default color Black.

To get what you want you must doublicate the specs:



FillingStyle -> {{Blue, Opacity[0.5]}, {Blue, Opacity[0.5]}}



Daniel





Nasser M. Abbasi wrote:

> Version 7 on windows XP sp2.

> 

> This is really a strange one, it seems like a "bug", but if not, then what 

> is it?

> 

> I have a function defined with UnitStep[]. I plot it using Plot and using 

> Filling->Axis.

> 

> The filling works ok across all the plot range even with different 

> FillingStyles for the color.

> 

> But when I use Opacity[] to change the filling Style more, then only _part_ 

> of the plot is now affected by the Opacity[]  and the other part is not.

> 

> Compare the following 2 plots to see:

> 

> y = -400*UnitStep[x - 100.8] + 8*(x - 63.4)*UnitStep[x - 63.4]

>      -8*(x - 43.2)*UnitStep[x - 43.2] + 221.3

> 

> Plot[y, {x, 0, 144},

>           Filling -> Axis,

>           FillingStyle -> {Opacity[0.5], Blue},

>           Frame -> True]

> 

> Plot[y, {x, 0, 144},

>          Filling -> Axis,

>          FillingStyle -> Blue,

>          Frame -> True]

> 

> --Nasser 

> 

> 




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