Re: [R] [EXT] Theta from negative binomial regression and power_NegativeBinomiial from PASSED

2023-09-14 Thread Andrew Robinson via R-help
Hi John,

the negative binomial is a tricky one - there are several different 
parameterisations and therefore different interpretations of the parameters.  
Joseph Hilbe wrote a whole book on it that might be wroth checking.

Cheers,

Andrew


--
Andrew Robinson
Chief Executive Officer, CEBRA and Professor of Biosecurity,
School/s of BioSciences and Mathematics & Statistics
University of Melbourne, VIC 3010 Australia
Tel: (+61) 0403 138 955
Email: a...@unimelb.edu.au
Website: https://researchers.ms.unimelb.edu.au/~apro@unimelb/

I acknowledge the Traditional Owners of the land I inhabit, and pay my respects 
to their Elders.
On 15 Sep 2023 at 11:52 AM +1000, Sorkin, John , 
wrote:
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Colleagues,

I want to use the power_NetativeBinomial function from the PASSED library. The 
function requires a value for a parameter theta. The meaning of theta is not 
given in the documentation (at least I can�t find it) of the function. Further 
the descriptions of the negative binomial distribution that I am familiar with 
do not mention theta as being a parameter of the distribution. I noticed that 
when one runs the glm.nb function to perform a negative binomial regression one 
obtains a value for theta. This leads to two questions

1. Is the theta required by the power_NetativeBinomial function the theta that 
is produced by the glm.nb function
2. What is theta, and how does it relate to the parameters of the negative 
binomial distribution?

Thank you,
John

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Re: [R] [EXT] Downloading a directory of text files into R

2023-07-25 Thread Andrew Robinson via R-help
Hi Bob,

there may be more efficient ways to go about it but I would use R to scrape the 
contents of

http://home.brisnet.org.au/~bgreen/Data/Hanson1/
http://home.brisnet.org.au/~bgreen/Data/Hanson2/

in order to form the URLs of the files, and then loop over the URLs.

Cheers,

Andrew

--
Andrew Robinson
Chief Executive Officer, CEBRA and Professor of Biosecurity,
School/s of BioSciences and Mathematics & Statistics
University of Melbourne, VIC 3010 Australia
Tel: (+61) 0403 138 955
Email: a...@unimelb.edu.au
Website: https://researchers.ms.unimelb.edu.au/~apro@unimelb/

I acknowledge the Traditional Owners of the land I inhabit, and pay my respects 
to their Elders.
On 26 Jul 2023 at 8:07 AM +1000, Bob Green , wrote:
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Hello,

I am seeking advice as to how I can download the 833 files from this
site:"http://home.brisnet.org.au/~bgreen/Data;

I want to be able to download them to perform a textual analysis.

If the 833 files, which are in a Directory with two subfolders were
on my computer I could read them through readtext. Using readtext I
get the error:

> x = readtext("http://home.brisnet.org.au/~bgreen/Data/*;)
Error in download_remote(file, ignore_missing, cache, verbosity) :
Remote URL does not end in known extension. Please download the
file manually.

> x = readtext("http://home.brisnet.org.au/~bgreen/Data/Dir/()")
Error in download_remote(file, ignore_missing, cache, verbosity) :
Remote URL does not end in known extension. Please download the
file manually.

Any suggestions are appreciated.

Bob

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Re: [R] [EXT] How to calculate the derivatives at each data point?

2023-01-31 Thread Andrew Robinson via R-help
Try something like

with(df, predict(smooth.spline(x = altitude, y = atm_values), deriv = 1))

Cheers,

Andrew

--
Andrew Robinson
Chief Executive Officer, CEBRA and Professor of Biosecurity,
School/s of BioSciences and Mathematics & Statistics
University of Melbourne, VIC 3010 Australia
Tel: (+61) 0403 138 955
Email: a...@unimelb.edu.au
Website: https://researchers.ms.unimelb.edu.au/~apro@unimelb/

I acknowledge the Traditional Owners of the land I inhabit, and pay my respects 
to their Elders.
On 31 Jan 2023 at 8:17 PM +1100, konstantinos christodoulou 
, wrote:
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Hi everyone,

I have a vector with atmospheric measurements (x-axis) that is
obtained/calculated at different altitudes (y-axis). The altitude is
uniformly distributed every 7 meters.
For example my dataframe is:
df <- dataframe(
*altitude* = c(1005, 1012, 1019, 1026, 1033, 1040, 1047, 1054, 1061, 1068),
*atm_values* = c(1.41, 1.40, 1.39, 1.38, 1.37, 1.37, 1.38, 1.36, 1.33, 1.31)
)

How can I find the derivatives of the atmospheric measurements at each
altitude?

I look forward to hearing from you!

Thanks,
Kostas

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