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Re: st: Re: Finding and graphing intersection of lines


From   Charles Vinis <charles.vinis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Re: Finding and graphing intersection of lines
Date   Wed, 3 Aug 2011 00:21:51 -0400

Thanks for the reply. I basically made a stata loop that gives
different market shares for firms (or average market shares by
country) based on a percentage point change in marginal cost for one
(or a group) of firms, then I reshape the set and use the data points
to make a line plot of the market share against the percent change in
marginal cost. Here's an example of the type of graph I'm doing: (I'm
using # delimit ; to end lines)

graph twoway line sim_comp_share pct_decrease_mc_fslr if(company ==
"first_solar" & year == 2010), color(brown)
|| line avg_ctry_comp_share  pct_decrease_mc_fslr if(ctry_code_hq ==
"usa" & year == 2010), color(green)
|| line avg_ctry_comp_share pct_decrease_mc_fslr if(ctry_code_hq ==
"china" & year == 2010), color(red)
|| line avg_ctry_comp_share pct_decrease_mc_fslr if(ctry_code_hq ==
"germany" & year == 2010), color(blue)
|| line avg_ctry_comp_share pct_decrease_mc_fslr if(ctry_code_hq ==
"taiwan" & year == 2010), color(purple)
ytitle(Market Share)
xtitle(Percent Decrease in First Solar MC)
legend(label(1 First Solar) label(2 USA) label(3 China) label(4
Germany) label(5 Taiwan));

Basically I would like for STATA to tell me exactly at which point
(what % decrease in MC and what market share) First Solar's market
share is equal to the average market share of a German or a Chinese
firm, and I would like to get stata to label that point on the graph.
Any ideas?

On Tue, Aug 2, 2011 at 5:21 PM, Anders Alexandersson
<andersalex@gmail.com> wrote:
> Could you please describe the line intersection problem more clearly,
> perhaps using a simple data example in Stata?
> Did you consider using the Stata graphics editor for editing the graphs?
>
> Anders Alexandersson
> andersalex@gmail.com
>
> Charles Vinis <charles.vinis@gmail.com> wrote:
>>> I'm currently developing an n-firm model of Cournot competition in which I am mapping the change in market shares between multiple companies based on reductions in marginal costs. I used a stata loop to find different market shares based on a 1-99 percent decrease in MC for the indicated firm, and I am graphing this as a line against the firms whose MCs are not decreasing. Because this is a program that I want people to be able to experiment with, I would prefer to find a way to get stata to find the intersection of the lines on its own so that I don't have to do it myself each time I run the calculations. I would like to be able to get the graph to label the point of intersection of these lines as well as to display the value of the x-axis and y-axis at that time. If anybody has any helpful ideas I would really appreciate it.
>
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