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# Re: st: 2 dimensional graph for joint distribution

 From Lulu Zeng <[email protected]> To [email protected] Subject Re: st: 2 dimensional graph for joint distribution Date Thu, 31 Oct 2013 11:44:34 +1100

```Dear Statalist

Thank you all for the valuable advices.

Given the bar chart is not an ideal representation as recommended by
most if you, and a 3D graph is need in my case, the user written
command by Andrian Mander -surface- could be an option for me as
suggested by some of you.

However, I am experiencing some trouble with surface graph. The graph
is not in a bell shape as expected, it's got very few data points on
the z axis and are sharp points.

All I did was: surface odo bill share

I suspect the issue is I need to calculate the joint probability for
odo and bill before graphing as oppose to graphing using share
directly (share gives the individual distribution for odo and bill).
Please note I have 1500 data points for each variable, the example I
gave in my earlier email is made up for demonstration.

automatically in the surface command? Also it would be appreciated if
you know any alternative way of doing the calculation and graph in one
go.

Thank you very much in advance!

Best Regards
Lulu

On Thu, Oct 31, 2013 at 1:54 AM, David Hoaglin <[email protected]> wrote:
> Lulu,
>
> That graph in Train's paper is definitely a type of display that one
> should avoid.
>
> Unless you have a fairly large number of combinations of the
> coefficients of odo and bill, you will have little way to develop the
> surface corresponding to the joint density function of those
> coefficients.
>
> For numbers of combinations like the six in your example, it might
> work to use a "bubble plot" --- a scatter plot of the coefficient of
> bill against the coefficient of odo in which each point is plotted as
> a circle whose area is proportional to share.  I don't know whether
> such a plot is readily available in Stata.
>
> Regards,
>
> David Hoaglin
>
> On Wed, Oct 30, 2013 at 7:07 AM, Lulu Zeng <[email protected]> wrote:
>> Dear Statalist
>>
>> I am having trouble creating a two dimensional joint distribution bar
>> graph in Stata.
>>
>> I'm trying to graph the joint distribution of 2 coefficients I
>> estimated from a nonparametric choice model using fixed mass point
>> method following Kenneth Train's approach in his 2008 paper (EM
>> Algorithms for nonparametric estimation of mixing distributions). The
>> graph I am trying to make is similar to the one on page 65 of Train's
>> paper: http://elsa.berkeley.edu/~train/EMtrain.pdf
>>
>> My 2 coefficients (both discrete) are called odo and bill, and the
>> variable share gives the distribution of the 2 coefficients (share
>> adds up to 1), for example:
>>
>> odo       bill        share
>> 0.25      0.58      0.15
>> 0.48      0.93      0.17
>> 0.33      0.20      0.09
>> 0.76      0.64      0.23
>> 0.87      0.28      0.25
>> 0.53      0.83      0.11
>>
>> I want to graph the joint distribution of odo and bill with them on
>> the x axis (2 dimensions), and their joint distribution shown as
>> percentages on the y axis.
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```