使用ggplot2在R中的箱线图

Question

I'm new to R and have been trying to make a boxplot. A part of the data I'm using is shown

            h1          h2          h3          h4          h5          h6          h7          h8          h9         h10
1  0.003719430 0.002975544 0.003049933 0.003421876 0.003421876 0.003347487 0.003645042 0.003496264 0.007364472 0.009075410
2  0.003400540 0.002749373 0.003038781 0.003328188 0.003328188 0.003400540 0.003472892 0.003400540 0.007741656 0.009333398
3  0.003741387 0.002918282 0.003142765 0.003367248 0.003367248 0.003367248 0.003666559 0.003516904 0.008081396 0.008156223
4  0.003870634 0.002884002 0.003187581 0.003339370 0.003567055 0.003415265 0.003794739 0.003491160 0.008348426 0.007741268
5  0.003782963 0.002950711 0.003177689 0.003480326 0.003404667 0.003404667 0.003707304 0.003631645 0.008927793 0.007414608
6  0.003643736 0.002884624 0.003264180 0.003416002 0.003491913 0.003416002 0.003871469 0.003795558 0.009033428 0.007135649
7  0.003718600 0.003035592 0.003111482 0.003339151 0.003566821 0.003566821 0.003642710 0.003870380 0.008120209 0.008044319
8  0.003819313 0.002979064 0.003284609 0.003360995 0.003590154 0.003437382 0.003895699 0.003590154 0.008326102 0.007791398
9  0.003899334 0.002981844 0.003211216 0.003364131 0.003669961 0.003440589 0.003746419 0.003669961 0.008410328 0.007569295
10 0.003828488 0.002986220 0.003292499 0.003445639 0.003522209 0.003522209 0.003598778 0.003598778 0.008422673 0.007810115

When I use the default boxplot command then this is what I get

boxplot(df)

I have been trying to generate the boxplot for same data using ggplot2 but it gives an error which I am unable to resolve. Here's what I tried.

library(ggplot2)
df <- readRDS('data.Rda')
ggplot(df) + geom_boxplot()

Here's the error

Don't know how to automatically pick scale for object of type data.frame. Defaulting to continuous
Error: Aesthetics must either be length one, or the same length as the dataProblems:df[, 6:15]

I saw the ggplot2 docs for geom_boxplot and realize (from the example) that I need to rearrange my data like

col1        col2
h1   0.003719430
h1   0.003400540
h1   0.003741387
h1   0.003870634
h1   0.003782963
h1   0.003643736
h2   0.002975544
h2   0.002749373
h2   0.002918282
h2   0.002884002
h2   0.002950711
h2   0.002884624
...

and use something like

ggplot(df, aes(factor(col1), col2)) + geom_boxplot()

But that is a lot of work. I believe that there must be some way to do this automatically which I'm not able to find. Any help is appreciated.

Answer 1

You are right ggplot requires your data to be reshaped, but it isn't that hard using the package reshape2 :

library(reshape2)
df <- melt(df)
ggplot(df, aes(x=variable, y=value)) + geom_boxplot()