Creating a boxplot, ggplot2

Question

I have the following data set:

depth <- data.frame(Sample = c("AD_001", "AD_009", "AD_017", "AD_025", 
                           "AD_033", "AD_041", "AD_049", "AD_057", 
                           "AD_065", "AD_073", "AD_081", "AD_089"), 
                median = c(12, 13, 11, 12, 12, 12, 13, 13, 14, 15, 15, 13), 
                granular_first_quartile = c(5, 6, 5, 6, 5, 6, 6, 6, 7, 7, 7, 6), 
                granular_third_quartile = c(23, 25, 21, 22, 23, 23, 24, 25, 27, 28, 28, 24))

and would like to create a boxplot but, the graphs I'm generating do not have an equally separated x field.

ggplot(depth, aes(as.factor(Sample))) + geom_boxplot(aes(middle = median, lower = granular_first_quartile, upper = granular_third_quartile, ymin = granular_first_quartile, ymax = granular_third_quartile), stat = 'identity') + coord_flip()

Thanks for the help!

the last example in ?geom_boxplot shows you how to make a boxplot from summary statistics. as does stackoverflow.com/questions/22212885/… — rawr
– rawr, Commented May 4, 2016 at 20:38
Your data have only one value of median per factor level in Sample. If you create a box plot of a single value, it will only return a line at that value, which I assume is what your plot looks like - a line at the value of median for each level of Sample. The plot wont have any whiskers. — capt-calculator
– capt-calculator, Commented May 4, 2016 at 21:00

Joonbum · Accepted Answer · 2016-05-04 20:53:59Z

2

You already have all (median, Q1, and Q3), and just need to assign lower, upper, middle, ymin, and ymax

(FYI, https://en.wikipedia.org/wiki/Box_plot#/media/File:Boxplot_vs_PDF.svg)

ggplot(depth, aes(Sample, median)) +
geom_boxplot(aes(lower = granular_first_quartile, upper = granular_third_quartile, 
middle = median, 
ymin = granular_first_quartile - 1.5*(granular_third_quartile-granular_first_quartile), 
ymax = granular_third_quartile+1.5*(granular_third_quartile-granular_first_quartile)),
stat="identity")+ coord_flip()

answered May 4, 2016 at 20:53

Joonbum

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2 Comments

kgui Over a year ago

great answer. I don't need the whiskers so I set the ymin and ymax to granular_first_quartile and granular_third_quartile, respectively. The only problem I have is that the x-axis is not being evenly spaced.

kgui Over a year ago

but, if I use your answer, the x-axis IS evenly spaced.

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