Can't use a y variable in aes_string

Question

I am currently working with COVID-19 data from Peru and I want to use a Rmisc::multiplot to show the development of positive cases in each region of the country. So I am trying to code a loop to generate 25 plots. Only as a matter of example I am only using 4 variables:

     Fecha    Lima     La Libertad  Madre de Dios
1 2020-04-24   10           2             1
2 2020-04-25   15           4             3
3 2020-04-26   20           8             3

I generated a vector with the names of the regions:

nombre_regiones <- c("Lima", "La Libertad", "Madre de Dios")

And I created an empty list to store the 25 plots within:

regiones <- list()

Then I used this for loop to generate and store each plot in the list "regiones":

for (w in seq_along(nombre_regiones)) { 
  nombre <- paste("r", w, sep = "")
  assign(nombre, ggplot(data = df, aes_string(x = "Fecha", y = nombre_regiones[w])) + geom_line() + geom_point() + scale_x_date(date_labels = "%d, %m", date_breaks  ="1 day") + geom_text(aes_string(label = nombre_regiones[w])))
  regiones[[w]] <- nombre
}

The loop created r1 and stored the plot within but when w = 2, that means nombre_regiones[w] = "La Libertad" I got the next warning:

Error in parse(text = x) : <text>:1:4: unexpected symbol
1: La Libertad
       ^

Because of that I can't create the second plot and the same thing happens with the third region "Madre de Dios". I tried different things and look up for similar cases but I didn't have luck. Also regiones[[w]] <- nombre isn't working but that's something I'll look up later. Thanks in advance.

Answer 1

It is better to initiate the list with full length

regiones <- vector('list', length(nombre_regiones))

Also, the aes_string is now deprecated. Instead, can be converted to symbol and evaluated (!!)

library(ggplot2)
for (w in seq_along(nombre_regiones)) { 
      nombre <- paste0("r", w)
      assign(nombre, ggplot(data = df,
          aes(x = Fecha, y = !! rlang::sym(nombre_regiones[w]))) +   
              geom_line() + 
              geom_point() + 
              scale_x_date(date_labels = "%d, %m", date_breaks  ="1 day") +
              geom_text(aes(label = !! rlang::sym(nombre_regiones[w]))))
      regiones[[w]] <- nombre
 }

-output r2

-output r3

data

df <- structure(list(Fecha = structure(c(18376, 18377, 18378), class = "Date"), 
    Lima = c(10L, 15L, 20L), `La Libertad` = c(2L, 4L, 8L), `Madre de Dios` = c(1L, 
    3L, 3L)), row.names = c("1", "2", "3"), class = "data.frame")