[R] (no answer)
I have never taken a statistics class nor read a statistics text, but
I am in dire need of help with a trivial data analysis problem for
which I need to write a report in two hours. I have spent 10,000
hours of study in my field of expertise (high frequency noise-making
plant biology) but I've always thought that statistics is something
that can be mastered on short notice.
Briefly, I have an experiment in which a response variable is
repeatedly measured at 1-day intervals, except that after a plant
becomes sick, it is measured every three days. We forgot to randomize
on one of the important variables (soil pH) and we forgot to measure
the soil pH. Plants that begin to respond to treatment are harvested
and eaten (deep fried if they don't look so good), but we want to make
an inference about long-term responses. In addition, we forgot to
measure the response on some of the days before the plant was
terminated. Some baseline variables were not measured for some
plants, when some of the other variables looked OK. The response
variable is only known to exceed a certain value in some cases, and in
others is only known to be less than a certain value. The response
variable also has a great number of ties at zero, and has extreme high
outliers. The variability of responses seems to depend on whether
there was missing variables for the plant. And halfway through the
experiment we changed instrumentation and personnel. All of these
problems seem trivial when compared to what I have to deal with every
day in measuring plant sounds, so I hope that someone can help me as
soon as possible. I would appreciate receiving a few paragraphs of
description of the analysis that I can include in my report, and I
would like to receive R code to analyze the data no matter which
variables I collect. I do value your time, so you will get my
everlasting thanks.
Note that I will be out of the office from 1:15pm to 1:25pm today.
This information should be valuable to many.
I. Ben Fuld
Technical University of Plant Kinetics
Slapout, Alabama
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Re: [R] (no answer)
On 01-Apr-06 Frank E Harrell Jr wrote:
I have never taken a statistics class nor read a statistics text, but
I am in dire need of help with a trivial data analysis problem for
which I need to write a report in two hours. I have spent 10,000
hours of study in my field of expertise (high frequency noise-making
plant biology) but I've always thought that statistics is something
that can be mastered on short notice.
Dear Ibn Fuld (I apologise for rewriting your name correctly,
and I do appreciate the problems of people who do not natively
speak English, but I thought that doind so would be useful for
the members of the list who have the coverse problem),
You have an evidently complex problem there, but apparently a
very short time in which to solve it. Happily, I see a very
simple solution.
Just talk to your plants, ask them how they are, record their
acoustic responses, and use your existing expertise to analyse
and interpret the latter. I judge that you need to learn nothing
new to do this, your institution should posses the required
technology, and I suspect that little if any new R code would be
required.
Good luck,
ZB [EMAIL PROTECTED]
Briefly, I have an experiment in which a response variable is
repeatedly measured at 1-day intervals, except that after a plant
becomes sick, it is measured every three days. We forgot to randomize
on one of the important variables (soil pH) and we forgot to measure
the soil pH. Plants that begin to respond to treatment are harvested
and eaten (deep fried if they don't look so good), but we want to make
an inference about long-term responses. In addition, we forgot to
measure the response on some of the days before the plant was
terminated. Some baseline variables were not measured for some
plants, when some of the other variables looked OK. The response
variable is only known to exceed a certain value in some cases, and in
others is only known to be less than a certain value. The response
variable also has a great number of ties at zero, and has extreme high
outliers. The variability of responses seems to depend on whether
there was missing variables for the plant. And halfway through the
experiment we changed instrumentation and personnel. All of these
problems seem trivial when compared to what I have to deal with every
day in measuring plant sounds, so I hope that someone can help me as
soon as possible. I would appreciate receiving a few paragraphs of
description of the analysis that I can include in my report, and I
would like to receive R code to analyze the data no matter which
variables I collect. I do value your time, so you will get my
everlasting thanks.
Note that I will be out of the office from 1:15pm to 1:25pm today.
This information should be valuable to many.
I. Ben Fuld
Technical University of Plant Kinetics
Slapout, Alabama
LEGAL NOTICE\ Unless expressly stated otherwise, this
messag...{{dropped}}
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E-Mail: (Ted Harding) [EMAIL PROTECTED]
Fax-to-email: +44 (0)870 094 0861
Date: 01-Apr-06 Time: 15:44:50
-- XFMail --
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Re: [R] (no answer)
Oh, and I forgot to add. Please generate some test data for me since
I can't possibly take time out to provide such in order to clarify the
question. By the way, I did try out R a bit but it did not work and its
too much effort to provide the R code I have or to reduce it to a small
self contained reproducible example to illustrate the salient point.
I am thanking you in advance since I will probably be too busy
to acknowledge the help or to summarize the answers for the
benefit of others and the list archives. Its not that I don't want to
but I probably won't follow up on your answers anyways if they involve reading
and thinking about help pages, the manual, the FAQ, the posting guide,
statistics, mathematics, programming or other material.
By the way, please email me directly since I normally don't read
the list.
:)
On 4/1/06, Frank E Harrell Jr [EMAIL PROTECTED] wrote:
I have never taken a statistics class nor read a statistics text, but
I am in dire need of help with a trivial data analysis problem for
which I need to write a report in two hours. I have spent 10,000
hours of study in my field of expertise (high frequency noise-making
plant biology) but I've always thought that statistics is something
that can be mastered on short notice.
Briefly, I have an experiment in which a response variable is
repeatedly measured at 1-day intervals, except that after a plant
becomes sick, it is measured every three days. We forgot to randomize
on one of the important variables (soil pH) and we forgot to measure
the soil pH. Plants that begin to respond to treatment are harvested
and eaten (deep fried if they don't look so good), but we want to make
an inference about long-term responses. In addition, we forgot to
measure the response on some of the days before the plant was
terminated. Some baseline variables were not measured for some
plants, when some of the other variables looked OK. The response
variable is only known to exceed a certain value in some cases, and in
others is only known to be less than a certain value. The response
variable also has a great number of ties at zero, and has extreme high
outliers. The variability of responses seems to depend on whether
there was missing variables for the plant. And halfway through the
experiment we changed instrumentation and personnel. All of these
problems seem trivial when compared to what I have to deal with every
day in measuring plant sounds, so I hope that someone can help me as
soon as possible. I would appreciate receiving a few paragraphs of
description of the analysis that I can include in my report, and I
would like to receive R code to analyze the data no matter which
variables I collect. I do value your time, so you will get my
everlasting thanks.
Note that I will be out of the office from 1:15pm to 1:25pm today.
This information should be valuable to many.
I. Ben Fuld
Technical University of Plant Kinetics
Slapout, Alabama
LEGAL NOTICE\ Unless expressly stated otherwise, this messag...{{dropped}}
__
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https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
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[R] (no answer)
I wish to perform brain surgery this afternoon at 4pm and don't know
where to start. My background is the history of great statistician
sports legends but I am willing to learn. I know there are courses and
numerous books on brain surgery but I don't have the time for those.
Please direct me to the appropriate HowTos, and be on standby for
solving any problem I may encounter while in the operating room. Some
of you might ask for specifics of the case, but that would require my
following the posting guide and spending even more time than I am
already taking to write this note.
I will be out of the office from 1:15pm to 1:25pm today. This
information should be valuable to many.
I. Ben Fooled
Technical University of Nonparametric Multivariate Statistics
Slapout, Alabama
---
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Re: [R] (no answer)
On Fri, 1 Apr 2005, Frank E Harrell Jr wrote:
I wish to perform brain surgery this afternoon at 4pm and don't know
where to start. My background is the history of great statistician
sports legends but I am willing to learn. I know there are courses and
numerous books on brain surgery but I don't have the time for those.
Please direct me to the appropriate HowTos, and be on standby for
solving any problem I may encounter while in the operating room. Some
of you might ask for specifics of the case, but that would require my
following the posting guide and spending even more time than I am
already taking to write this note.
Try:
help.search.google-function (string){
RURL = http://www.google.com/search;
RSearchURL = paste(RURL, ?sitesearch=r-project.orgq=,
string, sep = )
browseURL(RSearchURL)
return(invisible(0))
}
help.search.archive-function (string){
RURL = http://www.google.com/u/newcastlemaths;
RSearchURL = paste(RURL, ?q=, string, sep = )
browseURL(RSearchURL)
return(invisible(0))
}
help.start()
help.search.google(brain+surgery)
help.search.archive(brain+surgery)
Dave
--
Dr. David Forrest
[EMAIL PROTECTED](804)684-7900w
[EMAIL PROTECTED] (804)642-0662h
http://maplepark.com/~drf5n/
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Re:[R] (no answer)
Ben wrote: I wish to perform brain surgery this afternoon at 4pm and don't know where to start. My background is the history of great statistician sports legends but I am willing to learn. I know there are courses and numerous books on brain surgery but I don't have the time for those. ... It seems that you have aked the wrong list: R is not for that kind of things. My suggestion is: use SPSS: Surgery Procedures for Statistical Scientists: you'll almost certainly kill your patient but many surgery journals will accept to publish your results. Best regards, Sylvano Berillio --- Scegli il tuo dominio preferito e attiva la tua email! Da oggi l'eMail di superEva e' ancora piu' veloce e ricca di funzioni! http://webmail.supereva.it/new/ __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] wrong answer for simple expressions
Hi On 11 Nov 2004 at 12:24, Drew Hoysak wrote: I am experiencing strange (to me) output when trying to do simple calculations. Expressions that should equal zero yield non-zero values. Examples: a - 4.1-3.1 b - 5.1-4.1 a-b [1] -4.440892e-16 (4.1-3.1)-(5.1-4.1) [1] -4.440892e-16 When this last expression is expanded, I get the right answer: 4.1-3.1-5.1+4.1 [1] 0 I am using the binary packaged version R-2.0.0-0.fdr.1.fc2.i386.rpm for Linux Fedora Core 2. I had the same problem with version 1.9.0-0 Can anyone tell me what is going on? Floating point arithmetic is imprecise. Cheers Petr Thanks, Drew Hoysak __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Petr Pikal [EMAIL PROTECTED] __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
[R] wrong answer for simple expressions
I am experiencing strange (to me) output when trying to do simple calculations. Expressions that should equal zero yield non-zero values. Examples: a - 4.1-3.1 b - 5.1-4.1 a-b [1] -4.440892e-16 (4.1-3.1)-(5.1-4.1) [1] -4.440892e-16 When this last expression is expanded, I get the right answer: 4.1-3.1-5.1+4.1 [1] 0 I am using the binary packaged version R-2.0.0-0.fdr.1.fc2.i386.rpm for Linux Fedora Core 2. I had the same problem with version 1.9.0-0 Can anyone tell me what is going on? Thanks, Drew Hoysak __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] wrong answer for simple expressions
Drew Hoysak [EMAIL PROTECTED] writes: I am experiencing strange (to me) output when trying to do simple calculations. Expressions that should equal zero yield non-zero values. Examples: a - 4.1-3.1 b - 5.1-4.1 a-b [1] -4.440892e-16 (4.1-3.1)-(5.1-4.1) [1] -4.440892e-16 When this last expression is expanded, I get the right answer: 4.1-3.1-5.1+4.1 [1] 0 Welcome to the world of floating point arithmetic! Since one tenth cannot be represented exactly in binary, you are going to see these small deviations once in a while. It is is really no stranger than 3/3 - (1/3 + 1/3 + 1/3) = 1.000 - (0.333 + 0.333 + 0.333) = 0.001 in decimal notaion. -- O__ Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] wrong answer for simple expressions
On Thu, 11 Nov 2004, Drew Hoysak wrote: I am experiencing strange (to me) output when trying to do simple calculations. Expressions that should equal zero yield non-zero values. No. There is no reason why these expressions should yield zero values. Remember that computers work in base 2, and that 0.1 has an infinitely recurring binary expansion in base 2. You should expect that 0.1 computed two different ways should differ in the last few bits. You have managed to get zero to 52 bits accuracy, which is not bad when you consider that the machine only works to 54 bits. -thomas Examples: a - 4.1-3.1 b - 5.1-4.1 a-b [1] -4.440892e-16 (4.1-3.1)-(5.1-4.1) [1] -4.440892e-16 When this last expression is expanded, I get the right answer: 4.1-3.1-5.1+4.1 [1] 0 I am using the binary packaged version R-2.0.0-0.fdr.1.fc2.i386.rpm for Linux Fedora Core 2. I had the same problem with version 1.9.0-0 Can anyone tell me what is going on? Thanks, Drew Hoysak __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Thomas Lumley Assoc. Professor, Biostatistics [EMAIL PROTECTED] University of Washington, Seattle __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] wrong answer for simple expressions
R does double precision arithmetic and accumulates roundoff error like any other double precision computations. I would therefore expect it to accumulate roundoff error as you have reported. In most cases like you mentioned, a difference of 4e-16 is not material, to use Accounting jargon. If it is an issue, you either need to do error analysis or use something like Mathematica that does infinite precision arithmetic. hope this helps. spencer graves Drew Hoysak wrote: I am experiencing strange (to me) output when trying to do simple calculations. Expressions that should equal zero yield non-zero values. Examples: a - 4.1-3.1 b - 5.1-4.1 a-b [1] -4.440892e-16 (4.1-3.1)-(5.1-4.1) [1] -4.440892e-16 When this last expression is expanded, I get the right answer: 4.1-3.1-5.1+4.1 [1] 0 I am using the binary packaged version R-2.0.0-0.fdr.1.fc2.i386.rpm for Linux Fedora Core 2. I had the same problem with version 1.9.0-0 Can anyone tell me what is going on? Thanks, Drew Hoysak __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html -- Spencer Graves, PhD, Senior Development Engineer O: (408)938-4420; mobile: (408)655-4567 __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] wrong answer for simple expressions
On Thu, 2004-11-11 at 12:24 -0500, Drew Hoysak wrote: I am experiencing strange (to me) output when trying to do simple calculations. Expressions that should equal zero yield non-zero values. Examples: a - 4.1-3.1 b - 5.1-4.1 a-b [1] -4.440892e-16 (4.1-3.1)-(5.1-4.1) [1] -4.440892e-16 When this last expression is expanded, I get the right answer: 4.1-3.1-5.1+4.1 [1] 0 I am using the binary packaged version R-2.0.0-0.fdr.1.fc2.i386.rpm for Linux Fedora Core 2. I had the same problem with version 1.9.0-0 Can anyone tell me what is going on? A lack of understanding as to how floating point numbers are represented by computers under the IEEE 754 floating point standard. Hint: Take note of the following: print(0.1, digits = 20) [1] 0.1555 print(4.1, digits = 20) [1] 4.0996447 print(4.1 - 3.1, digits = 20) [1] 0.99955591 print(4.1 - 3.1 - 5.1, digits = 20) [1] -4.0996447 Read the last FAQ Why is 0.1 not 0.1? here: http://grouper.ieee.org/groups/754/faq.html#binary-decimal and read David Goldberg's article, What Every Computer Scientist Should Know about Floating-Point Arithmetic, which is available here: http://grouper.ieee.org/groups/754/ in a Postscript file or here in an edited form in HTML: http://docs.sun.com/source/806-3568/ncg_goldberg.html HTH, Marc Schwartz __ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
