2777 search results for "GIS"

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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R / Finance 2013 Open for Registration

March 29, 2013
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The annoucement below just went to the R-SIG-Finance list. More information is as usual at the R / Finance page: Now open for registrations: R / Finance 2013: Applied Finance with R May 17 and 18, 2013 Chicago, IL, USA The registration for R/Fin...

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Veterinary Epidemiologic Research: GLM (part 4) – Exact and Conditional Logistic Regressions

March 22, 2013
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Veterinary Epidemiologic Research: GLM (part 4) – Exact and Conditional Logistic Regressions

Next topic on logistic regression: the exact and the conditional logistic regressions. Exact logistic regression When the dataset is very small or severely unbalanced, maximum likelihood estimates of coefficients may be biased. An alternative is to use exact logistic regression, available in R with the elrm package. Its syntax is based on an events/trials formulation.

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Veterinary Epidemiologic Research: GLM – Evaluating Logistic Regression Models (part 3)

March 19, 2013
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Veterinary Epidemiologic Research: GLM – Evaluating Logistic Regression Models (part 3)

Third part on logistic regression (first here, second here). Two steps in assessing the fit of the model: first is to determine if the model fits using summary measures of goodness of fit or by assessing the predictive ability of the model; second is to deterime if there’s any observations that do not fit the

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The evolution of EU legislation (graphed with ggplot2 and R)

March 19, 2013
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The evolution of EU legislation (graphed with ggplot2 and R)

During the last half century the European Union has adopted more than 100 000 pieces of legislation. In this presentation I look into the patterns of legislative adoption over time. I tried to create clear and engaging graphs that provide … Continue reading →

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