R ggplot iterate through list of pollutants for graph titles

Question

I want to produce multiple graphs from a single dataframe listing different pollutant levels in different cities. I can loop through data slices without difficulty to plot pollutant levels, but I cannot create a different title for each graph in a loop. The graph titles include chemical formulae.

qdf = data.frame(x = rnorm(10), y = rnorm(10))
PolTitle <- expression(paste(NO[2], " pollutant values"))
MultiTitles = list(expression(paste(NO[2], " pollutant values")), 
   expression(paste(PM[2.5], " pollutant values")))
ggplot(qdf, aes(x,y)) + geom_point() + ggtitle(PolTitle)        # displays correctly
ggplot(qdf, aes(x,y)) + geom_point() + ggtitle(MultiTitles[2])  # unexpected parsing

correct graph title

incorrect graph title

score 1 · Answer 1 · answered Oct 04 '21 at 13:24

Use [[ instead of [ or use c instead of list:

qdf = data.frame(x = rnorm(10), y = rnorm(10))
PolTitle <- expression(paste(NO[2], " pollutant values"))
MultiTitles = list(expression(paste(NO[2], " pollutant values")), 
                   expression(paste(PM[2.5], " pollutant values")))
ggplot(qdf, aes(x,y)) + geom_point() + ggtitle(PolTitle)
ggplot(qdf, aes(x,y)) + geom_point() + ggtitle(MultiTitles[[2]])

R ggplot iterate through list of pollutants for graph titles

1 Answers1