Solved – Boxplot for several distributions

boxplotr

I need to draw 20 distributions in a single graph in R, and it doesn't look good (cluttered) to me with regular boxplot (20 boxes) even with boxwex=0.3. Could you suggest me how can I plot a kind of boxplot in R for the 20 distributions, with dots for median and just a line instead of box, like the one below. Please also suggest me if there is any R method that produces nice boxplots, specifically if you want to show several distributions in a single graph.

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Best Answer

(This is really a comment, but because it requires an illustration it has to be posted as a reply.)

Ed Tufte redesigned the boxplot in his Visual Display of Quantitative Information (p. 125, First Edition 1983) precisely to enable "informal, exploratory data analysis, where the research worker's time should be devoted to matters other than drawing lines." I have (in a perfectly natural manner) extended his redesign to accommodate drawing outliers in this example showing 70 parallel boxplots:

Tufte boxplots

I can think of several ways to improve this further, but it's characteristic of what one might produce in the heat of exploring a complex dataset: we are content to make visualizations that let us see the data; good presentation can come later.

Compare this to a conventional rendition of the same data:

Conventional boxplots

Tufte presents several other redesigns based on his principle of "maximizing the data ink ratio." Their value lies in illustrating how this principle can help us design effective exploratory graphics. As you can see, the mechanics of plotting them amounts to finding any graphics platform in which you can draw point markers and lines.

Related Solutions

Solved – What does this blur around the line mean in this graph

I suspect it means very little in your actual figure; you have drawn a form of stripplot/chart. But as we don't have the data or reproducible example, I will just describe what these lines/regions show in general.

In general, the line is the fitted linear model describing the relationship $$\widehat{\mathrm{val}} = \beta_0 + \beta_1 \mathrm{Num}$$ The shaded band is a pointwise 95% confidence interval on the fitted values (the line). This confidence interval contains the true, population, regression line with 0.95 probability. Or, in other words, there is 95% confidence that the true regression line lies within the shaded region. It shows us the uncertainty inherent in our estimate of the true relationship between your response and the predictor variable.

Solved – How to draw a boxplot without boxes in R

The stripchart function in the graphics library seems to be what you want if you want to plot the data 1 dimensionally for each group. It produces a somewhat basic plot but you can customize it

    business <- runif(50, min = 65, max = 100)
    law <- runif(50, min = 60, max = 95)
    df <- data.frame(group = rep(c("Business", "Law"), 
            each = 50), value = c(business, law), 
            stringsAsFactors = FALSE)
    
    stripchart(value ~ group, data = df, 
       main = "Salary Example (dots)",
       pch = 16,
       col = c("red", "green"))

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Related Solutions

Solved – What does this blur around the line mean in this graph

Solved – How to draw a boxplot without boxes in R

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