Plot lines in ggplot from a list of dataframes

Question

I have a list of data.frames:

samplelist = list(a = data.frame(x = c(1:10), y=rnorm(10),
                 b= data.frame(x=c(5:10), y = rnorm(5),
                 c = data.frame(x=c(2:12), y=rnorm(10))

I'd like to structure a ggplot of the following format:

ggplot()+ 
    geom_line(data=samplelist[[1]], aes(x,y))+
    geom_line(data=samplelist[[2]], aes(x,y))+
    geom_line(data=samplelist[[3]], aes(x,y))

But that isn't super automated. Does anyone have a suggestion for how to address this?

Thanks!

Answer 1

ggplot works most efficiently with data in "long" format. In this case, that means stacking your three data frames into a single data frame with an extra column added to identify the source data frame. In that format, you need only one call to geom_line, while the new column identifying the source data frame can be used as a colour aesthetic, resulting in a different line for each source data frame. The dplyr function bind_rows allows you to stack the data frames on the fly, within the call to ggplot.

library(dplyr)
library(ggplot2)

samplelist = list(a = data.frame(x=c(1:10), y=rnorm(10)),
                  b = data.frame(x=c(5:10), y=rnorm(6)),
                  c = data.frame(x=c(2:12), y=rnorm(11)))

ggplot(bind_rows(samplelist, .id="df"), aes(x, y, colour=df)) +
  geom_line()

I assumed above that you would want each line to be a different color and for there to be a legend showing the color mapping. However, if, for some reason, you just want three black lines and no legend, just change colour=df to group=df.