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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.

Boxplot

Can you help me please?

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  • $\begingroup$ You might want to log transform your data to better see their distribution. $\endgroup$
    – leoburgy
    Nov 22, 2018 at 13:52
  • $\begingroup$ There are plenty of zeros there, so I wouldn't use logarithm... $\endgroup$ Nov 22, 2018 at 14:14
  • $\begingroup$ This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review $\endgroup$ Nov 22, 2018 at 14:16
  • $\begingroup$ Forget the boxplot for a moment, and try summarizing the freq variable for each value of sex. $\endgroup$ Nov 22, 2018 at 14:30
  • $\begingroup$ Thanks for the advice. However the OP does not explicitly state that the low values displayed by the box plot are true zeroes. I thought that the log transform together with the other answers could 'help' the user as they states. Finally I don't have the feeling that I ask for further clarification in my answer. $\endgroup$
    – leoburgy
    Nov 22, 2018 at 14:39

2 Answers 2

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By default boxplot turns 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 with sex=1 are outliers in above sense.

Factor by which IQR is multiplied to obtain range of non-outliers is determined by range argument of boxplot function. Try experimenting with it. Plus, setting range=0 will force boxplot to treat all observations as non-outliers (whiskers will show min and max then).

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It seems that almost all values in group 1 equal zero, with a few positive values above the 75 percentile. So there is nothing wrong with your plot.

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