similar to: Calculating NOEL using R and logistic regression - Toxicology

Below. -- Bert On Tue, Apr 3, 2012 at 1:47 PM, Danielle Duncan <dlduncan2 at alaska.edu> wrote: > Thanks for the response, I should have clarified that the NOEL is the > smallest dose above which there is a statistically significant effect. > This is not a scientifically meaningful nor defensible definition as it is stochastic, depends on the test used, design, level chosen, etc.

Greetings, I have a question that I'd like to get input on. I have a classic toxicology study where I artificially fertilized and exposed embryos to a chemical and counted defects. In addition, I kept track of male-female pairs that I used to artificially fertilize and generate embryos with. I need to use logistic regression to model the response, but also check that the genetics of the

Classification: UNCLASSIFIED Caveats: NONE A similar question has been posted in the past but never answered. My question is this: for probit analysis, how do you program a 95% confidence interval for the LD50 (or LC50, ec50, etc.), including a heterogeneity factor as written about in "Probit Analysis" by Finney(1971)? The heterogeneity factor comes into play through the chi-squared

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I have been using R the past couple of years to run models on data we are collecting. I recently got a new computer and updated to a new version of R (2.60 -> 2.90). Since the update, I cannot get my syntax to run. I have tried copying the file it is looking for into many different directories to try and run it. In the last version, I found that it was easiest if the file was copied into the R

Hello, I am new to R. I often collect data at multiple sites and need to create separate graphs (such as scatterplots or histograms) of specific variables for each site. I have tried to do this by splitting the data frame and then using lapply, but it seems that the graphing commands cannot be called as functions. Here is a sample of my data, called "seeddist2": site

I am using the sink function to save several results (i.e. values of many different variables) to an output file. However, the output looks unattractive because it displays line numbers next to each new variable, it is difficult to remove the R variable name from the output, and I cannot print test without it using quotation marks. The only way I have found around most of these issues is to

Hi, I was wondering if someone could please help me. I am doing a logistic regression to compare size at maturity between 3 seasons. My model is: fit <- glm(Mature ~ Season * Size - 1, family = binomial, data=dat) where Mature is a binary response, 0 for immature, 1 for mature. There are 3 Seasons. The Season * Size interaction is significant. I would like to compare the size at 50%

Hello, I would like to use a permanova to analyze my repeated measures, multivariate data set using the package vegan (adonis function). I have several explanatory variables and many clinical biochemistry/hematological response variables (all continuous, non-normally distributed). My explanatory variables are: ID - 29 levels - individual subjects Treatment - 2 levels Sex - 2 levels Time -

Hi, I am trying to write a for loop with if else statements to calculate biomass density estimates for different types of sampling gear. My code is: bmd=for (i in 1:length(Gear)){ if (Gear==20) {bioden=Biomass/141} else {if (Gear==23) {bioden=Biomass/68}} else {if (Gear==160) {bioden=Biomass/4120}} else {if (Gear==170) {bioden=Biomass/2210}} else {if (Gear==300)

Hi, I appreciate you're busy so I just wanted to follow up on the email I sent you the other day, copy included below for reference. On Sat, Nov 12, 2016 at 12:40 PM, Danielle James <danielle.james at whoishostingthismail.com> wrote: Hi, I just wanted to let you know about a link that seems to be broken on this page http://www.hdt-project.org/. Here's the link

I have a comma delimited text file in which many columns of numbers are also quoted and have commas as well as decimals. I was surprised to find read.csv() didn't import this seamlessly, even after messing around with the colClasses argument. I did find a solution to convert the character strings after reading them in, but wonder if there isn't a better one I overlooked. test =

ok, i waited for 2 weeks, and still no votes -- none! -- on whether my posts are sufficiently on-topic, or not... and that basically confirms what i suspected all along, which is that no one really cares one way or the other. even the guys who put up the bitchy posts are probably just having a bad day, and they don't have a dog to kick, and the wife made 'em stop smoking herb, so they

Hi all, I'm having a strange error that prevents me from installing new packages, or updating packages after reinstalling. The error message is Warning: unable to move temporary installation ‘C:\Program Files\R\R-2.14.2\library\file15045004ac2\sandwich’ to ‘C:\Program Files\R\R-2.14.2\library\sandwich’ for one of the packages that is failing to install/update. This error started happening

Dear All: good morning I need helps with the calculation of the *LC50* from the data below x<-c(0,0.3,0.7,1,4,10) y<-c(100,86,65,51.3,19.2,7.4) yxreg<-lm(y~x) any help will be highly appreciated. with many thanks abou ______________________ *AbouEl-Makarim Aboueissa, PhD* *Professor of Statistics* *Department of Mathematics and Statistics* *University of Southern Maine*

I am attempting to estimate LC50 (analogous to LD50, but uses exposure concentration rather than dose) by fitting a Weibull model; but I can't seem to get it to work. From what I can gather, I should be using survreg() from the survival package. The survreg() function relies on time-to-event data; my data result from 96 h exposures (i.e., dead or alive after a fixed period; 96 h). I've

Hi, Is there anyone know if BUGS language allows the combination of variables as response such as Y[i] <- a*X1[i]+b*X2[i] Y[i] ~ dnorm(c,d) It seems doesn't work in my model. The problem is between two ######. The error message is > modelCheck("BayesBioMarker.BUGS") model is syntactically correct > modelData(paste("BUGS_data.txt",sep="")) data

Hi, I'm trying to do some basic social network analysis with igraph in R, but I'm new to R and haven't been able to find documentation on a couple basic things: I want to run igraph's community detection algorithms on a couple thousand small graphs but don't know how to automate igraph looking at multiple graphs described in a single csv file. My data look like something in

Sorry, spoke too quickly! The problem was caused by my editing the MkRules file with an editor that replaces tabs with spaces. Make evidently requires that all lines start with a tab (see http://www.delorie.com/djgpp/v2faq/faq22_17.html). Perhaps worth warning windoze users like myself of such perils in readme.packages or somewhere similar! Now I have a new problem, but it looks fixable.

Running dovecot 1.2.12 on ubuntu 10.10. Here is the problem: I have mysql backend for expire. I am using the dovecot-postfix package which creates /etc/dovecot/conf.d/01-mail-stack-delivery.conf which looks like this: # Some general options protocols = imap imaps managesieve disable_plaintext_auth = no ssl = yes ssl_cert_file = /etc/ssl/certs/ssl-mail.pem ssl_key_file =