# Plot outliers and their values

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The ‘*plot_outliers*‘ function below draws a **boxplot **and a **scatterplot **of a numeric variable *x* and plots the **values of the outliers** (currently not offset, even if they overlap). For relatively small datasets, it can be a quick way to identify which outliers look reasonable and which are likely a result of transcription or measurement error, and thus should be either corrected or discarded.

plot_outliers <- function(x, val_col = "blue", ...) { par_in <- par(no.readonly = TRUE) par(mfrow = c(1, 2)) bp <- boxplot(x, ...) out <- bp$out message(length(out), " outliers detected") if (length(out) > 0) text(x = 0.5, y = bp$out, labels = round(out, 2), adj = 0, col = val_col) plot(x, pch = 20) if (length(out) > 0) text(x = 0.5, y = bp$out, labels = round(out, 2), adj = 0, col = val_col) par(par_in) }

**Usage examples:**

plot_outliers(iris$Sepal.Width)

Additional arguments for the ‘*boxplot*‘ function can be provided, e.g.

plot_outliers(airquality$Ozone, notch = TRUE)

plot_outliers(airquality$Wind, col = "darkgreen", main = "wind")

This function is used in an article which we hope to submit soon.

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