similar to: testing goodness of fit of linear model

Dear R-users, There are tons of methods out there for fitting independant variables to a dependent variable. All stats books tell you about the assumptions behind OLS (ordinary least squares) and warn against abusive use of the method (which many of us do disregard by lack of a better knowledge). Most introductory text books stop there and don't tell you what the next best option might be. I

Dear R users, I am sorry to ask you such a pathetic newbie question, but how does one append data at the end of a data frame? I am working with GRASS/R library, but the question is about R. I have a data.frame containing the following variables basinID, distoutlet, drainage_area, slope These variables are stored for all pixels of Grass Raster objects. For each drainage basin (basinID), I'd

Hi all, I haven't been able to find how to assess a variable who's name is constructed with paste. The problem is following: In a data frame, there are 12 columns whose title vary only by a digit, all other part being equal. I would like to compute a operation on a subset these variables and parse them in turn. the data frame "basin.param" contains columns called ratio1,

I have a somewhat related question. A while back I was doing some simulations using for() loops, and I wanted to keep track of the iterations using a line of code quite similar to what Dimitris presented below. Instead of printing the iteration message at the end of each iteration (actually, at the end of every 100th), nothing was printed until the for() loop was complete, and *then* all

Dear R-users, I am puzzled by for loops and am kind of ashamed to ask because it is so simple. There must be something I am missing in the way they are executed. Basically, I would like to iterate a given number of time and generate a bunch of stats (that's what loops are designed for, right?). Before doing this I simply want to test simple procedure and see if they work (ie got the syntax

Hi there, I have two data sets, one of locations at different elevations (x,y,z) and the other of points that make up topographic contours (also x,y,z). I have used: result<-apply(distppll(data2,cbind(topocon[-nrow(topocon),],topocon[-1,])),1,min) where 'data2' are my measurement coordinates (x, y) and 'topocon' are my topographic contours (x,y). While this gives me an output

Hello! I need a function to compute the erosion of a binary image by a structuring element. I need the structuring element to be a ball of a given radius. As far as I know the libraries adehabitat and spatstat include functions of mathematical morphology but I couldn't find a function which computes the erosion by a ball. Any idea? Thanks!

I'm attempting to run 250 permutations of a negative binomial GLM model for data on fish counts. Many of the models are fit appropriately, but some issue warnings such as "convergence not reached" or "step size truncated due to divergence." I've attempted using glm.nb from the MASS package and the negbin function from the AOD package, but both still cause some models to

Hi Sherri, There are examples of topographic maps which you have been pointed to, however, I suspect that you want to know where you can obtain topographic data from rather than a canned example. There are quite a few intricacies to the process so I will go through them for you. (1) Topography files can be found in the geomapdata library. You will probably want to use the maps package too (if

Dear all, I wonder if anyone can help me with specifying a right model for my analysis. I am a beginner to lme methods. I was unfortunately not able to find a solution to my problem on my own. Data structure: I have sampled monthly 6 basins during two hydrological cycles, and I have taken several (2 to 4) samples (“replicate”) for each basin and month. I’m trying to relate Shannon diversity

Hi, I just imported two raster maps into R using the SPGRASS6 package, one containing elevation data and the other containing an erosion index: Kar_inc <-readRAST6("Incis_Kar", plugin=FALSE) Kar_dem <- readRAST6("DEM_Kar", plugin=FALSE) I just wanted to make a xy plot of erosion parameter vs elevation. How does this work? I don't get how to handle

Hello, I was hoping for some advice to resolve a problem I am having trouble with. The data consists of a series of pre and post variables, in a dataframe called 'offend'. I am interested in graphically depicting the pre & post values for a factor variable called 'decision' which has 4 values : nusm, fit, unsound & unfit. An example of a pre and post variable is:

One of many scripts to produce 4 lattice plots on one page keeps throwing an error. I've tried manipulating the file to eliminate the error, but have not been able to do so. The error is: > source('bicarb.R') Error in source("bicarb.R") : bicarb.R:15:1: unexpected symbol 14: 15: hco33 ^ The 'h' is in column 0 so the caret would be column -1, but it's

Can anyone help me? I''m having problems with the following code where I want to test the null hypothesis that regression slopes are the same among regressions. Here''s the code I''ve written with comments that include the final error I get. ... initial.dir <- getwd() library(systemfit) library(multcomp) basdata <- read.table("data_into7_test.txt",

I have tried glm.nb in the MASS package, but many models (I have 250 models with different combinations of predictors for fish counts data) either fail to converge or even diverge. I'm attempting to use the negbin function in the AOD package, but am unsure what to use for the "random" term, which is supposed to provide a right hand formula for the overdispersion parameter.

Dear list members I'm currently working on some topographic (elevation) data, and was somewhat surprised that the 'topo.colors' and 'terrain.colors' are of little to no use here. The problem is that these functions only return a palette of colours; they don't map depth values to colours. So if I plot (using 'image', 'persp' or similar functions) and

I will second Roger's suggestion, colorRampPalette is a great function for creating your own palettes. For example, Matlab's jet palette (also available in fields package under peculiar name 'tim.colors') can be defined by: jet.colors = colorRampPalette(c("#00007F", "blue", "#007FFF", "cyan", "#7FFF7F", "yellow",

I'm not sure I'm barking up the right tree here, but would I need to make use of groups to plot two separate datasets within ONE panel in xyplot? The desired end result is a single xy plot of two separate (but similar in values and ranges). Full code follows, xyplot code at bottom #########Determine Frequencies ##########coastal_slope #needs the maptools package to read ESRI grid

Hi, Am working on neural network. Below is the coding and the output > library (nnet) > uplift.nn<-nnet (PVU~ConsumerValue+Duration+PromoVolShare,y,size=3) # weights: 16 initial value 4068.052704 final value 3434.194253 converged > summary (uplift.nn) a 3-3-1 network with 16 weights options were - b->h1 i1->h1 i2->h1 i3->h1 16.64 6.62 149.93

Hello, I am hoping for some advice regarding warning/error messages I received when running a Cox regression # message 1 - obtained while creating a plot of residuals > plot (NV.zph, main = "groupNUSM - UNFIT", var= 'groupNUSM') Warning messages: 1: In approx(xx, xtime, seq(min(xx), max(xx), length.out = 17)[2 * : collapsing to unique 'x' values 2: In