Re: Discrete probablitiy distributions
- To: mathgroup at smc.vnet.net
- Subject: [mg16379] Re: [mg16273] Discrete probablitiy distributions
- From: "Tomas Garza" <tgarza at mail.internet.com.mx>
- Date: Thu, 11 Mar 1999 02:16:49 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Bjorn Leonardz wrote:
> I have been trying to find a good way of making Mathematica help me
> prepare some lecture notes in elementary probability. This is what I
> want to achieve:
>
> Given the probability function for a discrete random variable, e.g in
> the form of a list of probabilities
>
> 1. Plot the probability function (I can do this with ListPlot or
> BarChart)
>
> 2. Plot the cumulative probability function.
Hi Bjorn,
Suppose you have the list origprobs whose elements are {ai,pi}, for i =
1,...,m,
where pi is the probability of value ai.
Needs["Graphics`Graphics`"];
Needs["Statistics`DataManipulation`"];
You may plot the probability function with BarChart, as you say, using
BarChart[Transpose[{Transpose[origprobs][[2]],Transpose[origprobs][[1]]}]]
Use "CumulativeSums" from the add-on Statistics`DataManipulation` and get
BarChart[Transpose[{CumulativeSums[Transpose[origprobs][[2]]],Transpose[orig
probs][[1]]}]]
You can also plot the distribution function (i.e. the cumulative probability
function) in the traditional (and more useful) way as follows:
distfunc =
Interpolation[Transpose[{Transpose[origprobs][[1]],CumulativeSums[Transpose[
origprobs][[2]]]}], InterpolationOrder->0}
and then
Plot[distfunc[x, {x,Min[a1],Max[ai]}]
Good luck,
Tomas Garza
Mexico City