343 search results for "evaluation"

Sobol Sensitivity Analysis

June 10, 2013
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Sobol Sensitivity Analysis

Sensitivity analysis is the task of evaluating the sensitivity of a model output Y to input variables (X1,…,Xp). Quite often, it is assumed that this output is related to the input through a known function f :Y= f(X1,…,Xp). Sobol indices are generalizing the coefficient of the coefficient of determination in regression. The ith first order indice is the proportion of...

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Flotsam 12: early June linkathon

June 1, 2013
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A list of interesting R/Stats quickies to keep the mind distracted: A long draft Advanced Data Analysis from an Elementary Point of View by Cosma Shalizi, in which he uses R to drive home the message. Not your average elementary point of view. Good notes by Frank Davenport on starting using R with data from

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Item Analysis App – Shiny Code

May 28, 2013
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Item Analysis App – Shiny Code

Here is the code for my first Shiny App! It is the one that I posted previously with a few slight revisions. You can see it at:A Shiny R AppIn order to make any sense of this I suggest you working through the tutorial (http://www.rstudio.com/shiny/) it...

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Why doesn’t R have a MaxDiff package?

May 28, 2013
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Almost once every year someone asks if R has a package for running the MaxDiff procedure sold by Sawtooth.  One such inquiry recently received a reply with a link showing in some detail the R code needed to generate a balanced incomplete...

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(Another) introduction to R

May 27, 2013
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(Another) introduction to R

It’s Memorial Day and my dissertation defense is tomorrow. This week I’m phoning in my blog. I had the opportunity to teach a short course last week that was part of a larger workshop focused on ecosystem restoration. A fellow grad student and I taught a session on Excel and R for basic data analysis.

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Shiny + Concerto = YES !!!

May 23, 2013
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Shiny + Concerto = YES !!!

So I have finally gotten beta access to the two most powerful R controlled web application makers in existence and produced very exciting experimental productsA few posts ago I posted a Visual Reasoning Test that I had made by hand and powered wit...

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Model fitting exam problem

May 20, 2013
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Recently I have run an exam where the following question had risen many problems for students (here I give its shortened formulation). You are given the data generating process y = 10x + e, where e is error term. Fit linear regression using lm, ne...

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awalé

May 12, 2013
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awalé

Following Le Monde puzzle #810, I tried to code an R program (not reproduced here) to optimise an awalé game but the recursion was too rich for R: even with a very small number of holes and seeds in the awalé… Searching on the internet, it seems the computer simulation of a winning strategy for

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Feature Selection 2 – Genetic Boogaloo

May 8, 2013
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Feature Selection 2 – Genetic Boogaloo

Previously, I talked about genetic algorithms (GA) for feature selection and illustrated the algorithm using a modified version of the GA R package and simulated data. The data were simulated with 200 non-informative predictors and 12 linear effects and three non-linear effects. Quadratic discriminant analysis (QDA) was used to model the data. The last set of...

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Feature Selection Strikes Back (Part 1)

April 29, 2013
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Feature Selection Strikes Back (Part 1)

In the feature selection chapter, we describe several search procedures ("wrappers") that can be used to optimize the number of predictors. Some techniques were described in more detail than others. Although we do describe genetic algorithms and how they can be used for reducing the dimensions of the data, this is the first of series of blog posts that...

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