To illustrate applications of *auditor* to regression problems we will use an artificial dataset apartments available in the *DALEX* package. Our goal is to predict the price per square meter of an apartment based on selected features such as construction year, surface, floor, number of rooms, district. It should be noted that four of these variables are continuous while the fifth one is a categorical one. Prices are given in Euro.

```
library(DALEX)
data("apartments")
head(apartments)
```

```
## m2.price construction.year surface floor no.rooms district
## 1 5897 1953 25 3 1 Srodmiescie
## 2 1818 1992 143 9 5 Bielany
## 3 3643 1937 56 1 2 Praga
## 4 3517 1995 93 7 3 Ochota
## 5 3013 1992 144 6 5 Mokotow
## 6 5795 1926 61 6 2 Srodmiescie
```

```
lm_model <- lm(m2.price ~ construction.year + surface + floor + no.rooms + district, data = apartments)
```

```
library("randomForest")
set.seed(59)
rf_model <- randomForest(m2.price ~ construction.year + surface + floor + no.rooms + district, data = apartments)
```

The beginning of each analysis is creation of a `modelAudit`

object. Itâ€™s an object that can be used to audit a model.

```
library("auditor")
lm_audit <- audit(lm_model, label = "lm", data = apartmentsTest, y = apartmentsTest$m2.price)
rf_audit <- audit(rf_model, label = "rf", data = apartmentsTest, y = apartmentsTest$m2.price)
```

Model performance measures may be plotted together to easily compare model performances.

Function `modelPerformance()`

compute chosen model performance measures. A result further from the center means a better model performance.

```
lm_mp <- modelPerformance(lm_audit, scores = c("MAE", "MSE", "REC", "RROC"))
rf_mp <- modelPerformance(rf_audit, scores = c("MAE", "MSE", "REC", "RROC"))
lm_mp
```

```
## score label name
## 1 2.633246e+02 lm MAE
## 2 8.013798e+04 lm MSE
## 3 2.632619e+02 lm REC
## 4 3.244698e+12 lm RROC
```

Results of `modelPerformance()`

function for multiple models may be plotted together on one plot.
Parameter `table`

indicates whether the table with scores should be generated.

On the plot scores are inversed and scaled to [0,1].

```
plot(lm_mp, rf_mp, table = TRUE)
```

There is a possibiliy to define functions with custom model performance measure.

```
new_score <- function(object) sum((object$residuals)^3)
lm_mp <- modelPerformance(lm_audit,
scores = c("MAE", "MSE", "REC", "RROC"),
new.score = new_score)
rf_mp <- modelPerformance(rf_audit,
scores = c("MAE", "MSE", "REC", "RROC"),
new.score = new_score)
plotModelRanking(lm_mp, rf_mp, table = TRUE)
```

Other methods and plots are described in vignettes: