search for: mike_saunders

Is there a package, or does anyone have code they are willing to share, that would allow me to simulate sampling of dead wood pieces across an area? I am specifically looking for code to simulate the dead wood distribution as small line segments across an extent, and then I will "sample" the dead wood using different sampling techniques including line transects, fixed area plots, etc.

Just a quick question. Is there a way to easily specify factor levels in a function definition within nls? For example, I am trying to fit a 3 parameter, nonlinear Weibull function to tree height and I would like to have results by species (or down the road a bit, by plot). I am hoping there is someway to do it easily, similar to the "gas example" in the ANCOVA chapter in Modern

Could someone give me a hand with the format of the gsummary function? Basically, I have a large set of xyz coordinates generated by LiDAR data (>37 million points) and I am trying to derive various summary statistics on the z-coordinates by a grid cell. I wrote a function to do this by creating factors from the x- and y- coordinates and then using gsummary. However, I want the function to

This is a strange request, but I want to build a scatterplot using different image files (jpegs, gif, etc.) as the plot symbols. I have thought about setting this up using a very large layout matrix, but I thought someone might have a better approach. Furthermore, is there any way to have R paste an image file into a specific coordinate within a scatterplot? Thanks in advance, Mike Mike

I wish to do a stacked area chart to show how relative proportions of species within a stand have changed over time. I know this is simple, but can someone point me to the right function (if it exists). I have not had any luck finding it in the R-help, but maybe I am searching using the wrong keywords. Thanks, Mike Mike Saunders Research Assistant Forest Ecosystem Research Program Department

Does someone out there have an example of R-code for a split-split plot ANOVA using aov or another function? The design is not balanced. I never set up one in R before and it would be nice to see an example before I tackle a very complex design I have to model. Thanks, Mike Mike Saunders Research Assistant Forest Ecosystem Research Program Department of Forest Ecosystem Sciences University of

I know this is a long shot, but does anyone out there have code for converting a R-dataframe into a Stand Visualization System (SVS) tree list? It would save me a bit of time. I would be interested if anyone has FVS code as well. I will be working (reworking) NE-TWIGS equations to a regionwide dataset. Thanks in advance, Mike Mike R. Saunders Forest Biometrician Cooperative Forest Research

I am modeling a trend surface using trmat and want to trim the resulting matrix to the area enclosed by my real data (i.e., remove all the extrapolated areas). I was using chull and in.chull to calculate the convex hull and change all the other values created by trmat to NA. However, my real data has portions that are slightly concave so chull would give me slivers that are extrapolations from

Hi, I am rather new to R, but both myself and another much more experience user cannot figure this out. I have a collegue who has a 800+ nonlinear regressions to run for seed germination (different species, treatments, etc.) over time. I created a looping structure to extract the parameters from each regression; I will then use the parameters themselves for further analysis. I would like to

I ran into a problem with "subset" while working at home that I am not sure is a bug or not. I defined a custom function to take a data frame of tree positions, sizes, and types (containing the columns TRT, COMP, PLOT, X, Y, DBH and CON) and wanted to make a stem map of the plot using different symbols and colors to represent the different types of tree stems. I copied a bit of the

R community: I have been creating code for plotting nomographs, or multiple, overlain contour plots of z-variables on a common x- and y- variable. My input has been a matrix with observed x, y, and multiple z variables; I then create a trend surface using trmat for each z-variable. So far so good. One application I have for these, requires shading a portion of the nomogram that meets criteria