lapply with boxplots in R

问题

I am trying to use lapply to create many box plots in R. When I create the box plots using a ggplot function I get the correct output. When I try to pass the box plot function through the lapply using colnames the function does not work as expected. The correct plot and the incorrect plot examples are attached.

doPlot = function(var1) {

  # Create the plot object
  ggobj = ggplot(wdbc_train, aes(x = diagnosis,y=var1)) + geom_boxplot()

  # Add some titles and axis labels
  ggobj = ggobj + ggtitle(var1) + xlab("diagnosis") + 
    ylab(var1)
}

lapply(colnames(wdbc_train),doPlot)

Correct

correct

Incorrect

incorrect

回答1:

You need to get the data from the named variable.

doPlot = function(var1) {

  # Create the plot object 
  ggobj = ggplot(wdbc_train, aes(x = diagnosis, y=get(var1))) + 
    geom_boxplot()

  # Add some titles and axis labels 
  ggobj = ggobj + ggtitle(var1) + xlab("diagnosis") + ylab(var1) 
}

doPlot = function(var1) {

  # Create the plot object 
  ggobj = ggplot(iris, aes(x = Species, y=get(var1))) + geom_boxplot()

  # Add some titles and axis labels 
  ggobj = ggobj + ggtitle(var1) + xlab("Species") + ylab(var1) 
}

p <- lapply(colnames(iris)[-5], doPlot)

library(gridExtra)
grid.arrange(grobs=p)

回答2:

When you pass var1 to the function doPlot it is just a string. It needs to be interpreted as a column of the dataframe.

We can use non-standard evaluation (NSE) with sym and !! here.

library(ggplot2)
library(rlang)

doPlot = function(df, var1) {
  # Create the plot object
  ggobj = ggplot(df, aes(diagnosis,y = !!sym(var1))) + geom_boxplot()
  # Add some titles and axis labels
  ggobj + ggtitle(var1) + xlab("diagnosis") + ylab(var1)
}

then apply it for every column which would give you list of plots in list_plot.

list_plot <- lapply(colnames(wdbc_train), doPlot, df = wdbc_train)

Previously this was possible using aes_string wherein you could pass a column name as a string but this has been deprecated.

来源：https://stackoverflow.com/questions/61585360/lapply-with-boxplots-in-r

标签

ggplot2

lapply