892 search results for "how to import image file to R"

Measuring persistence in a time series : Application of rolling window regression

Measuring persistence in a time series : Application of rolling window regression

During my final semester at IGIDR I did a project paper in macroeconomics involving timeseries econometrics. The concept that I focused on my study was unit root, which I have touched upon in my earlier posts. This study presents a novel...

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Plotting 95% Confidence Bands in R

July 24, 2012
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Plotting 95% Confidence Bands in R

I am comparing estimates from subject-specific GLMMs and population-average GEE models as part of a publication I am working on. As part of this, I want to visualize predictions of each type of model including 95% confidence bands. First I … Continue reading →

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What’s wrong with LOESS for palaeo data?

July 24, 2012
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What’s wrong with LOESS for palaeo data?

Locally weighted scatterplot smoothing (LOWESS) or local regression (LOESS) is widely used to highlight “signal” in variables from stratigraphic sequences. It is a user-friendly way of fitting a local model that derives its form from the data themselves rather than having … Continue reading →

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A comparison of some heuristic optimization methods

July 23, 2012
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A comparison of some heuristic optimization methods

A simple portfolio optimization problem is used to look at several R functions that use randomness in various ways to do optimization. Orientation Some optimization problems are really hard. In these cases sometimes the best approach is to use randomness to get an approximate answer. Once you decide to go down this route, you need … Continue reading...

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Modeling Permanent and Gradual Process Changes with CDFs

July 20, 2012
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Modeling Permanent and Gradual Process Changes with CDFs

Spencer HerathSpecial thanks to Ben OgorekBackgroundI recently faced a process with a structural change resulting in an increase in the process mean.  The jump to the new mean was not immediate; rather, there was a gradual increase in values over time.  I had previously benefited from multi-staged process-behavior charts when encountering immediate process shifts, but now I needed a...

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Time zones

July 18, 2012
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Time zones

Say we have some following raw data. It consists of a timestamp and a corresponding value. There is a peak at exactly midnight (00:00:00). Each timestamp is fully specified. It contains a date, a time of day, and a time zone offset indication. In this case +0000, meaning the data is 0 hours away the UTC timezone. "timestamp","value""25-04-2012...

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R for Ecologists: Creating a Site x Species Matrix

July 17, 2012
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R for Ecologists: Creating a Site x Species Matrix

Today I’m going to adress a fairly common problem in ecology that has been coming up frequently as of late. The issue is how to create a site x species matrix for community composition analysis (i.e. ordination). Moreover, ecologists have to do … Continue reading →

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Hierarchical Cluster Analysis (ChemoSpec) – 01

July 17, 2012
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Hierarchical Cluster Analysis (ChemoSpec) – 01

I have been in previous post using the ChemoSpec package for some oil data (olive and sunflower). My spectra has now a range from 1100nm to 2200nm and is raw (not treated mathematically) . I want to start using the ChemoSpec package to start using the ...

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Processing Public Data with R

July 13, 2012
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Processing Public Data with R

I use R aplenty in analysis and thought it might be worthwhile for some to see the typical process a relative newcomer goes through in extracting and analyzing public datasets In this instance I happen to be looking at Canadian air pollution statistics. The data I am interested in is available on the Ontario Ministry

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