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Re: y-axis direction

  • To: mathgroup at smc.vnet.net
  • Subject: [mg116556] Re: y-axis direction
  • From: Helen Read <readhpr at gmail.com>
  • Date: Sat, 19 Feb 2011 05:15:07 -0500 (EST)
  • References: <ijisli$27u$1@smc.vnet.net> <ijlek0$r5b$1@smc.vnet.net>

On 2/18/2011 4:37 AM, telefunkenvf14 wrote:
> On Feb 17, 4:18 am, "Rob Y. H. Chai"<yhc... at ucdavis.edu>  wrote:
>> Hi all,
>>
>> In the Plot command, the convention for y-axis is up for positive values.  Is
>> there an easy way to reverse the y-axis direction i.e. pointing down for
>> increasing positive y values? Thanks.
>>
>> Rob Chai
>
> I have encountered the same problem... economists like to graph
> inverse demand and supply equations (i.e., price(quantity)) rather
> than the true relationship of quantity(price).
>
> Possible ways around this:
>
> (1) solving for the inverse relationship and then using Plot[] (one
> could also use InverseFunction[] ---- not always straightforward as
> your function may not be clearly invertible w/o providing assumptions
> on parameters)
> (2) using ContourPlot[], which incorporates the functionality of the
> legacy function ImplicitPlot (you can still use ImplicitPlot; search
> documentation for details)
>
> For the most part, I've settled on (1).

I think the OP is talking about something else, keeping the y-axis 
vertical but with reversed orientation on the y-axis (to which others 
have posted solutions).

But for what you are talking about, I would suggest (3) ParametricPlot. 
That is, if you have x=f(y) make a ParametricPlot of {f[y],y}


-- 
Helen Read
University of Vermont


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