search for: meandecreasegini

HI, Dear Andy, I run the RandomFOrest in R, and get the following resutls in variable importance: What is the meaning of MeanDecreaseAccuracy and MeanDecreaseGini? I found they are raw values, they are not scaled to 1, right? Which column if most similar to the variable rel.influence in Boosting? Thanks so much! > fit$importance 0 1 MeanDecreaseAccuracy MeanDecreaseGini CT 0.0022352025 0.003829344...

...Windows, there are small numeric deviations when using the 32- / 64-bit version of R, which doesn't seem to be a problem on Linux or Mac. R64 on Windows produces the same results as R64/R32 on Linux or Mac: > set.seed(131) > importance(randomForest(Species ~ ., data=iris)) MeanDecreaseGini Sepal.Length 9.452470 Sepal.Width 2.037092 Petal.Length 43.603071 Petal.Width 44.116904 R32 on Windows produces the following: > set.seed(131) > importance(randomForest(Species ~ ., data=iris)) MeanDecreaseGini Sepal.Length 9.433986 Sepal...

Hi All, In the script below, the importance measure for column 4 (ie MeanDecreaseGini) indicated "Inf" for V7. Running the getTree command showed that "V7" had been selected at least twice in one of the trees for Random Forest. So the "Inf" command was not generated as a result of dividing the sum of the decreases by 0. Any suggestions on what may be...

I am trying to use the random forests package for classification in R. The Variable Importance Measures listed are: -mean raw importance score of variable x for class 0 -mean raw importance score of variable x for class 1 -MeanDecreaseAccuracy -MeanDecreaseGini Now I know what these "mean" as in I know their definitions. What I want to know is how to use them. What I am trying to figure out is what these values mean in only the context of how accurate they are, what is a good value, what is a bad value, what are the maximums and minimums, etc....

...rmutated data error and the original test set error) 1 - mean raw importance score of variable x for class 1 MeanDecreaseAccuracy : average lowering of the margin across all cases (where margin is the proportion of votes for the true class - the maximum proportion of votes for the other classes) MeanDecreaseGini : summation of the gini decreases over all trees in the forest Are these definitions correct? Why is the raw importance score calculated for each class? Could one just average the raw importance scores for class 0 and 1 to get a composite importance score? Now, when having the option &quo...

For anyone who is knowledgeable about the randomForest package in R, I have a question: When I look at the variable importance for data, I see that my response variable is included along with my predictor variables. That is, I am getting a MeanDecreaseGini for my response variable, and therefore it seems as though it is being treated as a predictor variable. my code (just in case it helps) : comm.RF<-randomForest(model.data,y=model.data$Comm_Heir,mtry=8,importance=T) Apologies if it's a stupid question, but I'm new to randomForests. Hope...