similar to: help with syntax of nlme function

This may appear too elementary to some on this list, but not to me. My apologies if this is the case. I have mastered the lme function but the nlme function has me stumped. I am attempting to fit a nonlinear mixed model with 4 levels of nesting. I am getting a cryptic error message and do not know what is wrong with the syntax of the call. This is the call: >

Hello. I am trying to fit a nonlinear mixed model involving 3 parameters. I have successfully made a self-starting function. getInitial() correctly outputs the initial estimates. I can also use the nlsList with this function to get the separate nonlinear fits by group. However, I get an error message when using the nlme function. Here is the relevent code:

I am getting an error message in a call to nlme and cannot understand what is happening. I explain the steps below in the hope that someone can explain the error and how to correct it. STEP 1: Data set: name: marouane.data. This is a data frame whose first few lines are as follows: > marouane.data[1:13,] species plant leaf irradiance photosynthesis chlorophyll 1

Hello R-gurus, I'm trying to adjust different growth curves to a rather extensive dataset. I wrote up a function to go through all of them, but am encountering a problem : among the more than 1000 curves I have, obviously for some of them I encounter conversion problems. I'd like for my function to keep going to the next curve and store the fact that for curve number X I had a convergence

Sorry for disturbing you with another newbie question! I have a data frame about coastal waters quality parameters: for some parameters (e.g. NH3) I have only 1 observation for each sampling station and each sampling date, while in other cases (chlorophyll) I have 1 obs for each meter-depth for each station and date. How can I select only the max chlorophyll value for each station/date? example

Hi, I would be very grateful for some advice. I have read the help pages for Date, strptime, etc. All examples seem to use some version of day month year as date format. However I have Weekly composite data so ONLY want to input the dates as Week.Year (eg 35.2011). strptime seems to show this is possible using %W for week (UK convention) and %Y for year. My data is in a df called chlorophyll and

Hello all, I can't seem to figure how to use a greek character in expression() in plot() labels without adding a space. So for example below when plotting this out x<-1:10 plot(x,x^2, xlab=expression(Chlorophyll~italic(a)~mu~g~cm^-2)) the axis label read as μ g cm^-2 because I have space there with a tilda. But if I remove the tilda then my units are mug cm^-2. Can anyone recommend a

DateTime,Temp,SpCond,DOConc,Depth,pH,ORP,Turbidity+,Chlorophyll,Battery,Cond,DO%,Salinity,TDS 01/13/2006 17:01,10.87,84,9.36,0.664,7.3,132,28.8,3.1,11.5,0.062,84.6,0.04,0.055 01/13/2006 17:16,10.9,84,9.36,0.66,7.31,133,28.7,2.9,11.5,0.062,84.7,0.04,0.055 01/13/2006 17:31,10.92,84,9.36,0.655,7.3,132,28.4,2.6,11.4,0.062,84.8,0.04,0.055 01/13/2006

Hi, I am looking at the effects of two explanatory variables on chlorophyll. The data are an annual time-series (so are autocorrelated) and the relationships are non-linear. I want to account for autocorrelation in my model. The model I am trying to use is this: Library(mgcv) gam1 <-gam(Chl~s(wintersecchi)+s(SST),family=gaussian, na.action=na.omit, correlation=corAR1(form =~

Hi All, I'm using the following code to produce some stacked bar graphs. *setwd("C:\\Users\\Tinus\\Documents\\NMMU\\R\\Seamounts")* *SChla <- read.csv("SM_Chla_data.csv")* * * *#Extract mean values from data file* * * *Coral <- SChla[185:223,] #Reduce SChla to Coral only* *coral <- with(Coral , aggregate(cbind(Pico, Nano, Micro), list(Depth),FUN=mean))*

Hi, I wonder if anybody could help me in converting this easy SAS program into R. (I'm still trying to do that!) PROC IMPORT OUT= WORK.CHLA_italian DATAFILE= "C:\Documents and Settings\carleal\My Documents\REBECCA\stat\sas\All&nutrients.xls" DBMS=EXCEL2000 REPLACE; GETNAMES=YES; RUN; data chla_italian; set chla_italian;

Hello, I would like to evaluate the relationship between flows and phytoplankton abundance (or Chlorophyll a concentrations) using a changepoint analysis.? Specifically, I have two study questions: Study Question 1: Are there certain flow thresholds that result in spikes in phytoplankton abundance? Study Question 2: Are the duration of certain flows important for phytoplankton abundance (e.g.,

Hello. I had previously posted a question concerning the optimization of a nonlinear function conditional on equality constraints. I was pointed towards the contrOptim function. However, I do not understand the syntax of this function with respect to specifying the constraints and so I don’t know if it is what I need. The command is: constrOptim(theta, f, grad,ui,ci,…). “theta” is the

Hello, and Happy New Year. My default working directory is getting very cluttered. I know that I should be using a different working directory for each project (I work in Windows), but do not know how to go about creating different ones and moving back and forth between them. I have read Venables & Ripley (Modern Applied Statistics with S-PLUS, 1994) but this seems out of date with respect

Hello. Please excuse this off-topic request, but I know that the question has been debated in summary form on this list a number of times. I would find a paper that lays out the advantages and disadvantages of using different types of SS in the context of unbalanced data in ANOVA, regression and ANCOVA, especially including the use of different types of contrasts and the meaning of the

Hello. I am trying to determine whether I should be using ML or REML methods to estimate a linear mixed model. In the book by Pinheiro & Bates (Mixed-effects models in S and S-PLUS, page 76) they state that one difference between REML and ML is that « LME models with different fixed-effects structures fit using REML cannot be compared on the basis of their restricted likelihoods. In

Hello, and please excuse this off-topic question, but I have not been able to find an answer elsewhere. Consider a value Z that is calculated using the product (or ratio) of two means X_mean and Y_mean: Z=X_mean*Y_mean. More generally, Z=f(X_mean, Y_mean). The standard error of Z will be a function of the standard errors of the means of X and Y. I want to calculate this se of Z. Can someone

Hello. I have a script in which I repeatedly fit a nonlinear regression to a series of data sets using nls and the port algorithm from within a loop. The general structure of the loop is: for(i in 1:n){ … extract relevant vectors of dependent and independent variables … … estimate starting values for Amax and Q.LCP…

Hello. I am sorry for posting a (seemingly) simple question, but I have just spent 2 hours trying to find the answer, without success. I want to make a histogram with conditioning on a factor, using Trellis graphics. However, I do not want any colours (only black and white) either in the histograms or in the strip. There must be some simple argument but I can’t find it. Here is my code so

To avoid angry replies, let me first say that I know that the use of Type III sums of squares is controversial, and that some statisticians recommend instead that significance be judged using the non-marginal terms in the ANOVA. However, given that type III SS is also demanded by some… is there a function (equivalent to drop1 for lm) to obtain type III sums of squares for mixed models using the