boxplotr
I have a rather mysterious problem when I try to do a simple boxplot with
boxplot(data$sex,data$freq)
but I'm unable to display box plot, and I cannot figure out why.
The type of my variable are respectively factor and numeric, and the dataset is composed of 40.000 observations.
Can you help me please?
Something like this?
library(ggplot2)
ggplot(Final, aes(x = as.factor(Tod), y = Temp)) + geom_boxplot() + facet_wrap(~ Loc)
Interpretation of the box plot (alternatively box and whisker plot) rests in understanding that it provides a graphical representation of a five number summary, i.e. minimum, 1st quartile, median, 3rd quartile and maximum. The box encompasses 50% of the observations. The ends of the whiskers (vertical lines emanating from the top and bottom of the box) typically show where the minimum and maximum lie. However, where possible outliers exist (sometimes assessed based on 1.5 $\times$ interquartile range) points are added, as is the case for your figure.
It may be useful for you to look at a histogram or density plots on specific categories of the data as that may help you understand what the box plot is saying.
@Glen_b rightly indicates that left skew is evident and the central tendency for the 5th level of strength of feeling is lower than the others. It is difficult however to see whether that difference would be statistically significant or not.
Best Answer
By default
boxplotturns into points all outliers, which are defined as the datapoints that are farther that 1.5*IQR from box (IQR = Quartile3-Quartile1). So probably almost all observations withsex=1are outliers in above sense.Factor by which IQR is multiplied to obtain range of non-outliers is determined by
rangeargument ofboxplotfunction. Try experimenting with it. Plus, settingrange=0will forceboxplotto treat all observations as non-outliers (whiskers will show min and max then).