Iris is very famous dataset, containing only 150 measurements. But how much measurements do you need to predict what kind of iris is new one? Select number of measurements in training set by slider. We use GBM to predict other species by only two parameters: sepal width and length. Dataset contains also petal width and length, but we are using only sepal parameters now.
https://hokumski.shinyapps.io/predicting-iris-species-by-sepals/