Displaying 20 results from an estimated 3000 matches similar to: "Nonnormal Residuals and GAMs"
2006 Oct 27
3
R & gams
At office I have been introduced by another company to new, complex energy
forecasting models using gams as the basic software.
I have been told by the company offering the models that gams is specialised
in dealing with huge, hevy-weight linear and non-linear modelling (see an
example in http://www.gams.com/modtype/index.htm) and they say it is almost
the only option for doing it.
I would
2011 Oct 13
3
Question about GAMs
hi! I hope all of you can help me this question
for example GAMs:
ozonea<-gam(newozone~
pressure+maxtemp+s(avetemp,bs="cr")+s(ratio,bs="cr"),family=gaussian
(link=log),groupA,methods=REML)
formula(ozonea)
newozone ~ pressure + maxtemp + s(avetemp, bs = "cr") + s(ratio,bs = "cr")
#formula of gams
coef(ozonea) # extract the coefficient of GAMs
2011 Sep 28
2
GAMs in R : How to put the new data into the model?
I have 5 GAMs ( model1, model2, model3, model4 and model5)
Before I use some data X(predictor -January to June data) to form a equation
and calculate the expected value of Y (predictand -January to June). After
variable selection, GAMs (Model 1)were bulit up! R-square :0.40
NOW, I want to use new X'( predictor -July - December data) and put into
Model 1, then get the expected value of Y'
2012 Jan 16
2
Object not found using GAMs in MGCV Package
This is my first time running GAMs in R.
My csv file has these column headings:
"X" "Y" "Sound" "Atlantic" "Blacktip" "Bonnet"
"Bull" "Finetooth" "Lemon" "Scalloped" "Sandbar" "Spinner"
"Abundance" "Diversity"
2007 Apr 08
1
Relative GCV - poisson and negbin GAMs (mgcv)
I am using gam in mgcv (1.3-22) and trying to use gcv to help with model selection. However, I'm a little confused by the process of assessing GCV scores based on their magnitude (or on relative changes in magnitude).
Differences in GCV scores often seem "obvious" with my poisson gams but with negative binomial, the decision seems less clear.
My data represent a similar pattern as
2008 Nov 15
1
GAMs and GAMMS with correlated acoustic data
Greetings
This is a long email.
I'm struggling with a data set comprising 2,278 hydroacoustic estimates of
fish biomass density made along line transects in two lakes (lakes
Michigan and Huron, three years in each lake). The data represent
lakewide surveys in each year and each data point represents the estimate
for a horizontal interval 1 km in length.
I'm interested in comparing
2012 Jul 11
2
Modifying the design matrix X in GAMS to suit data assimilation
I have a data assimilation problem that might be amenable to the use of GAMS, but I am not sure how feasible it is to implement. I was told the R mailing list was a great resource.
My observations are spatiotemporal salinity in the San Francisco Bay at a number of instruments over a few days. The thing that I want to fit is the initial condition for a salt transport model at the beginning of this
2012 Nov 27
1
interactions in GAMs
Hi all,
I wonder if it's possible to include a double interaction in a GAM formula.
Example:
If I do this:
mod=gam(energy~s(size, *by=color, by=sex*, k=5) + temperature, ...)
I get the interaction betwen size*color and size*sex.
But I need size*color*sex, being size a smoother.
I've created a new variable (colorsex) which combines all the level of both
color (2 levels) and sex (2
2002 Nov 13
2
Comparing GAM objects using ANOVA
Hi,
Is it possible to compare two GAM objects created with the gam() function from the mgcv package. I use a slightly modified version of anova.glm() named anova.gam(), modified from John Fox (2002). It often gives me some aberant responses, especially with "F" test. I use a quasibinomial model and scale (dispersion) is calculated and used in the calculation of the F value. Does someone
2010 Apr 06
1
GAMs and survival data
Hello. I'm trying to analyze data, which is looking at the relationship between temperature and survival for fish (from fertilization to emergence). Looking at the raw data, there appears to be a bell shaped relationship. Ordinarily for survival data, I would run a generalized linear model (because the data has a binomial error structure). However, I am thinking that running a generalized
2007 Aug 14
1
weights in GAMs (package mgcv)
Dear list,
I?m using the ?mgcv? package to fit some GAMs. Some of my covariates are
derived quantities and have an associated standard error, so I would
like to incorporate this uncertainty into the GAM estimation process.
Ideally, during the estimation process less importance would be given to
observations whose covariates have high standard errors.
The gam() function in the ?mgcv? package
2008 Mar 21
1
GAMs
Hi
I have been searching for goodness-of-fit tests (or lack of fit tests) for GAMs and cannot find anything.
My problem is: after fitting a GAM to mortality data (smoothing crude estimated rates of mortality - a process called graduation in the actuarial literature), (1) how to assess the fit of the model with reference to "adherence to data" for the fitted model (I do not think the
2007 Jun 15
1
interpretation of F-statistics in GAMs
dear listers,
I use gam (from mgcv) for evaluation of shape and strength of relationships
between a response variable and several predictors.
How can I interpret the 'F' values viven in the GAM summary? Is it
appropriate to treat them in a similar manner as the T-statistics in a
linear model, i.e. larger values mean that this variable has a stronger
impact than a variable with smaller F?
2006 Nov 28
4
GAMS and Knots
Hi
I was wondering if anyone knew how to work out the number of knots that
should be applied to each variable when using gams in the mgcv library?
Any help or references would be much appreciated.
Thanks
Kathryn Baldwin
2009 Jun 23
1
How to find b entries using xPath?
We got all rows by:
library(XML)
doc =
htmlParse('http://www.statcan.gc.ca/daily-quotidien/090520/t090520b1-eng.htm')
rows = xpathSApply(doc, '//table/tbody/tr')
The last row is:
row_last = rows[15]
row_last
[[1]]
<tr><td id="t1stub17" class="stub1 RGBShade"><b>Unsmoothed composite
leading indicator</b></td>
<td
2006 Nov 03
4
read file problem
R-help,
I have the following file I want to import to R (some lines
removed)
Calibrated CTD data for station:00280001
Calibrated:23/8 2001, Salinity Unsmoothed, Fluorescence Uncalibrated
Maximum observed depth: 36 m
QUAL has one digit for each of pressure, temp., sal. and fluor.
QUAL=1:Uncal., QUAL=2:OK, QUAL=6:Interp., QUAL=9:No data
2008 Aug 14
1
autocorrelation in gams
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 =~
2018 Sep 19
2
Bias in R's random integers?
El mi?., 19 sept. 2018 a las 14:43, Duncan Murdoch
(<murdoch.duncan at gmail.com>) escribi?:
>
> On 18/09/2018 5:46 PM, Carl Boettiger wrote:
> > Dear list,
> >
> > It looks to me that R samples random integers using an intuitive but biased
> > algorithm by going from a random number on [0,1) from the PRNG to a random
> > integer, e.g.
> >
2007 Jul 24
2
plotting gam models
Hi everybody,
I am working with gams and I have found some questions when plotting gams models.
I am using mgcv, and my model looks something like this:
model<- gam(x ~ s(lat,long))
I can plot the output of the model using plot(model) or plot.gam(model) and I get a surface plot.
That is ok, but what I want to do now is to extract the data used to perform the surface plot. Like that I
2009 Apr 04
2
Help using smooth.spline with zoo object
Can someone please show me how to smooth time series data that I have in the form of a zoo object?
I have a monthly economies series and all I really need is to see a less jagged line when I plot it.
If I do something like
s <- smooth.spline(d.zoo$Y, spar = 0.2)
plot(predict(s,index(d.zoo)), xlab = "Year")
# not defined for Date objects
and if I do something like