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## Regression Trees

The discussion so far has dwelt on classification trees. Regression trees are similarly well catered for in R.

We can plot regression trees as with classification trees, but the node information will be different and some options will not make sense. For example, extra= only makes sense for 100 and 101.

First we will build regression tree:

target <- "risk_mm"
vars <- c(inputs, target)
form <- formula(paste(target, "~ ."))
(model <- rpart(formula=form, data=ds[tr, vars]))
 ```## n=120710 (3012 observations deleted due to missingness) ## ## node), split, n, deviance, yval ## * denotes terminal node ## ## 1) root 120710 8520917.0 2.250133 ## 2) humidity_3pm< 83.5 112949 3473217.0 1.466297 ## 4) humidity_3pm< 67.5 95894 1848947.0 1.004440 * ## 5) humidity_3pm>=67.5 17055 1488802.0 4.063149 * ## 3) humidity_3pm>=83.5 7761 3968362.0 13.657610 ## 6) rainfall< 23.1 6929 2035563.0 11.241620 ## 12) min_temp< 22.45 6552 1455940.0 10.268640 * ## 13) min_temp>=22.45 377 465620.4 28.151460 * ## 7) rainfall>=23.1 832 1555527.0 33.778250 ## 14) min_temp< 20.35 605 646342.8 25.438180 * ## 15) min_temp>=20.35 227 754946.3 56.006170 ## 30) humidity_3pm< 95.5 179 350412.6 45.052510 * ## 31) humidity_3pm>=95.5 48 302966.0 96.854170 * ```