jitter error

[J H]

Hi- I noticed that if I use geom_boxplot, I see in addition, single data points outside the boxes, which is OK.  however, when I include geom_jitter, the data points within the boxes now become visible, which is fine, however, the jitter adds duplicate data only for those points outside of the boxes.  How can I get around this?  Thanks.

[Dennis Murphy]

The usual remedy is to suppress the points outside the box inside the
boxplot; try

... + geom_boxplot(..., outlier.colour = NA)

where ... is a placeholder for other pertinent code. You have to use
the Commonwealth spelling, since outlier.color = NA has no effect.

Dennis

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[Richard Zijdeman]

Hi, this basically is what Murphy's says: but here are some examples of what might go wrong and how to fix it when combining box plots and a jittered geom_point plot:

# load library

library(ggplot2)

# draw a boxplot with '+' symbol for outliers

p <- ggplot(mtcars, aes(factor(cyl), mpg))

p1 <- p + geom_boxplot(outlier.shape=3)

p1

# overlay with points (with horizontal jitter)

p1 + geom_point(position = position_jitter(width=0.2))

# this indeed provides duplicate outlier points

# fix duplicates, by not showing outliers in initial boxplot

p2 <- p + geom_boxplot(outlier.colour=NA)

p2 + geom_point(position = position_jitter(width=0.2))

# overlay boxplots on geom_points: points or obscured

p3 <- p + geom_point(position = position_jitter(width=0.2))

p3 +  geom_boxplot(outlier.colour=NA)

# remove fill of box plots to uncover obscured points:

p3 + geom_boxplot(outlier.colour=NA, fill = NA)

Best,

Richard