Re: [R] QQ plotting of various distributions...

2009-09-27 Thread Petar Milin
Thanks for the answer. Now, only problem is to to get parameter(s) of a given function. For gamma, I shall try with gammafit() from mhsmm package. Also, I shall look for others appropriate parameter estimates. Will use SuppDists too. Best, PM Sunil Suchindran wrote: #same shape some_data -

Re: [R] QQ plotting of various distributions...

2009-09-27 Thread Eric Thompson
The supposed example of a Q-Q plot is most certainly not how to make a Q-Q plot. I don't even know where to start First off, the two Q:s in the title of the plot stand for quantile, not random. The answer supplied simply plots two sorted samples of a distribution against each other. While

Re: [R] QQ plotting of various distributions...

2009-09-27 Thread Duncan Murdoch
Eric Thompson wrote: The supposed example of a Q-Q plot is most certainly not how to make a Q-Q plot. I don't even know where to start First off, the two Q:s in the title of the plot stand for quantile, not random. The answer supplied simply plots two sorted samples of a distribution

Re: [R] QQ plotting of various distributions...

2009-09-27 Thread Juliet Hannah
I think it's helpful to show the sampling variability in a QQ plot under repeated sampling. An example is given in Venables, Ripley pg 86. The variance is higher at the tails. Even when the distributions are the same, the QQ plot does not have to resemble a straight line because of sampling. I

Re: [R] QQ plotting of various distributions...

2009-09-27 Thread Petar Milin
Thanks all! I did not want to cause any trouble and, God forbid, offense. I thought, I asked a simple question to improve my understanding and R-skills. It seems that there ain't single gospel truth about QQs. :-) Thanks, again! Best, PM Juliet Hannah wrote: I think it's helpful to show the

Re: [R] QQ plotting of various distributions...

2009-09-27 Thread Eric Thompson
It seems I misunderstood Sunil's response and somewhat freaked out because it appeared that he was giving the wrong method for making a QQ plot, but was actually demonstrating the sampling variability. My apologies to Sunil. 2009/9/27 Duncan Murdoch murd...@stats.uwo.ca: Eric Thompson wrote:

Re: [R] QQ plotting of various distributions...

2009-09-25 Thread Sunil Suchindran
#same shape some_data - rgamma(500,shape=6,scale=2) test_data - rgamma(500,shape=6,scale=2) plot(sort(some_data),sort(test_data)) # You can also use qqplot(some_data,test_data) abline(0,1) # different shape some_data - rgamma(500,shape=6,scale=2) test_data - rgamma(500,shape=4,scale=2)

[R] QQ plotting of various distributions...

2009-09-17 Thread Petar Milin
Hello! I am trying with this question again: I would like to test few distributional assumptions for some behavioral response data. There are few theories about true distribution of those data, like: normal, lognormal, gamma, ex-Gaussian (exponential-Gaussian), Wald (inverse Gaussian) etc. The