similar to: Dates - week and year not day.

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

I am having difficulty understanding the syntax of the nlme() function for nonlinear mixed models. The data frame is called Marouane.chlorophyll. The model involves a dependent variable (Absorb) and an independent variable (Ch.surf), which are both numeric variables in the data frame. The data are hierarchically grouped as Espece, Plante nested within Espece, and Feuille nested within Plante

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.,

Dear users I am fitting a Generalized Additive Mixed Models (gamm) model to establish possible relationship between explanatory variables (water temperature, dissolved oxygen and chlorophyll) and zooplankton data collected in the inner and outer estuarine waters. I am using monthly time-series which are auto-correlated. In the case of the inner waters, I have applied satisfactoryly (by

Hello, I am a new user to R and have a(proabably very basic) question relating to a boxplot with eleven sites in a river system where i measured Chlorophyll a concentrations. The eleven sites are made up of three sites above a point source pollution site; three sites below this pollution source and five sites in a different unaffected river. The following code is for a simple plot of the data

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