2577 search results for "gis"

R for Ecologists: RLQ analysis (semi) explained

September 3, 2013
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R for Ecologists: RLQ analysis (semi) explained

I’ve been reading about RLQ analysis, also known as the fourth corner method, for analyzing relationships between environmental characteristics and species traits. I was interested because I thought I might be using RLQ analysis to answer a specific set of … Continue reading →

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Estimation, prediction, and evaluation of logistic regression models

August 26, 2013
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I provide an introduction to using logistic regression for prediction (binary classification) using the Titanic data competition from www.Kaggle.com as an example. I use models to predict in missing data, estimate a logistic regression model on a trai...

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Residuals from a logistic regression

August 23, 2013
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Residuals from a logistic regression

I always claim that graphs are important in econometrics and statistics ! Of course, it is usually not that simple. Let me come back to a recent experience. A got an email from Sami yesterday, sending me a graph of residuals, and asking me what could be done with a graph of residuals, obtained from a logistic regression ?...

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Analyse discriminante linéaire ou Regression logistique

July 10, 2013
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Analyse discriminante linéaire ou Regression logistique

Supposons que l'on dispose d'iris de Paris (en population >100khabts) et qu'on veuille pouvoir les classer selon leurs caractéristiques sociodémos : Population taux de chômage Etudiants CSP etc... Une fois, les iris classés, on se demande si l'on peut transporter cette typologie à une autre grande ville (Lyon) par exemple : Il faudrait alors pouvoir utiliser un modèle d'affectation des iris selon leurs caractéristiques respectives...

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Getting raster histogram in QGIS using SEXTANTE and R

July 6, 2013
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Getting raster histogram in QGIS using SEXTANTE and R

The issue with the broken histogram creation tool in QGIS annoyed me far too long. Sometimes you just need a quick glance on the histogram of a raster just to make a decision on how to process it or just to assess distribution of classes. But as you kn...

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R GIS: Terrain Analysis for Polygons as Simple as it Gets!

June 18, 2013
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R GIS: Terrain Analysis for Polygons as Simple as it Gets!

library(rgdal)library(raster)alt gadm gadm_sub plot(alt)plot(gadm_sub, add=T)asp slo > extract(slo, gadm_sub, fun = mean, na.rm = T, small = T, df = T) ID slope1 1 9.9590532 2 1.0474433 3 7.4561654 4 1.6737865 5 11.946553> extract(asp, gadm_sub, fun = mean, na.rm = T, small...

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Robust logistic regression

June 7, 2013
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Corey Yanofsky writes: In your work, you’ve robustificated logistic regression by having the logit function saturate at, e.g., 0.01 and 0.99, instead of 0 and 1. Do you have any thoughts on a sensible setting for the saturation values? My intuition suggests that it has something to do with proportion of outliers expected in the The post Robust...

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How logistic regression work ?

May 31, 2013
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How logistic regression work ?

Discussing with a non statistician colleague, it seems that the logistic regression is not intuitive; Some basics questions like : - Why don't use the linear model? - What's logistic function? - How can we compute by hand, step by step t...

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Creating a QGIS-Style (qml-file) with an R-Script

May 6, 2013
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Creating a QGIS-Style (qml-file) with an R-Script

How to get from a txt-file with short names and labels to a QGIS-Style (qml-file)? I used the below R-script to create a style for this legend table where I copy-pasted the parts I needed to a txt-file, like for the WRB-FULL (WRB-FULL: Full soil code o...

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R/Finance 2013 Registration Open

March 29, 2013
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The registration for R/Finance 2013 -- which will take place May 17 and 18 in Chicago -- is NOW OPEN!Building on the success of the previous conferences in 2009, 2010, 2011 and 2012, we expect more than 250 attendees from around the world. R users from...

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