Trying to make a list of ggplot objects in a for loop; all items in list are written as last iteration from loop [duplicate]

Answer 1

Subset the data frame before calling ggplot, and then use aes_string to call column names as string.

library(ggplot2)

l <- list()
for(i in 2:11){
  temp <- mtcars[, c(1, i)]
  p <- ggplot(temp, aes_string(x = "mpg", y = names(temp)[2])) + geom_smooth() + geom_point()
  name <- paste("p",i,sep="_")
  tmp <- list(p)
  l[[name]] <- tmp
}
print(l$p_2)

print(l$p_3)

Answer 2

You can create a list of plots directly using sapply. For example:

plist = sapply(names(mtcars)[-grep("mpg", names(mtcars))], function(col) {
  ggplot(mtcars, aes_string(x = "mpg", y = col)) + geom_smooth() + geom_point()
}, simplify=FALSE)

The list elements (each of which is a ggplot object) will be named after the y variable in the plot:

names(plist)

[1] "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear" "carb"

You can print all the plots by typing plist in the console. Or, for a single plot, just select the plot you want:

plist[["hp"]]

For a situation like this, you might prefer faceting, which requires converting the data from wide to long format. You can have facets with different y scales by setting scales="free_y".

library(tidyverse)

ggplot(gather(mtcars, key, value, -mpg), aes(mpg, value)) + 
  geom_smooth() + geom_point() +
  facet_wrap(~ key, scales="free_y", ncol=5)