2811 search results for "gis"

Residuals from a logistic regression

August 23, 2013
By
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 ?...

Read more »

Analyse discriminante linéaire ou Regression logistique

July 10, 2013
By
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...

Read more »

Getting raster histogram in QGIS using SEXTANTE and R

July 6, 2013
By
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...

Read more »

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

June 18, 2013
By
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...

Read more »

Robust logistic regression

June 7, 2013
By

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...

Read more »

How logistic regression work ?

May 31, 2013
By
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...

Read more »

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

May 6, 2013
By
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...

Read more »

R/Finance 2013 Registration Open

March 29, 2013
By

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...

Read more »

R / Finance 2013 Open for Registration

March 29, 2013
By

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...

Read more »

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

March 22, 2013
By
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.

Read more »