Cant save ggplot graphs while using a loop in R

Question

For some reason, I can't figure out, why when I run a ggplot loop to create multiple graphs I don't see them in the environment and hence can't further display the graphs. Data sample.

db = data.frame(exposure = sample(1:100, 100),
                   exposure2 = sample(-90:100,100),
                   outcome = sample(200:1000,100))

exposure_vector = c("exposure","exposure2")
exposure_title = c("Pesticide","Apple")
for (i in 1:length(exposure_vector)) {
  current_exposure = db[[exposure_vector[i]]]
  title = exposure_title[i]
  graph_name = paste0(title,"_","Graph")
  graph_name=ggplot(db,aes(x=current_exposure,y=outcome))+geom_smooth()+
    theme_bw()+ylab("outcome")+xlab("exposure")+ggtitle(title)
  print(graph_name)
  
  
}

George Savva · Accepted Answer · 2022-12-01 09:48:05Z

1

This is probably a better way to do what you are trying to do. You can mapply over your vectors of titles and exposures, which will return a list of graphs you can then refer to by name:

graphs <- mapply(X=exposure_title,Y=exposure_vector, function(X,Y){
  
  ggplot(db,aes(x=.data[[Y]],y=outcome))+
    geom_smooth()+
    theme_bw()+
    ylab("outcome")+
    xlab("exposure")+
    ggtitle(X)

}, SIMPLIFY = FALSE )

graphs$Pesticide

graphs$Apple

edited Dec 1, 2022 at 9:48

answered Dec 1, 2022 at 9:34

George Savva

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Comments

geom_na · Accepted Answer · 2022-12-01 07:31:52Z

0

The graphname is out of scope.

You need to declare it outside the loop.

For example

db = data.frame(exposure = sample(1:100, 100),
                exposure2 = sample(-90:100,100),
                outcome = sample(200:1000,100))

exposure_vector = c("exposure","exposure2")
exposure_title = c("Pesticide","Apple")

plot <- list() #declare
for (i in 1:length(exposure_vector)) {
  current_exposure = db[[exposure_vector[i]]]
  title = exposure_title[i]
  graph_name = paste0(title,"_","Graph")
  graph_name=ggplot(db,aes(x=current_exposure,y=outcome))+geom_smooth()+
    theme_bw()+ylab("outcome")+xlab("exposure")+ggtitle(title)
  
  plot[[i]] <- graph_name #write
  print(graph_name)
  
  
}

answered Dec 1, 2022 at 7:31

geom_na

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Comments

Stefano Barbi · Accepted Answer · 2022-12-01 08:05:03Z

I assume that you want to assign to a variable, whose name is paste0(title, "_", "Graph"), the value of the plot. If this is correct, you should use assign

library(ggplot2)

db <- data.frame(exposure = sample(1:100, 100),
                 exposure2 = sample(-90:100,100),
                 outcome = sample(200:1000,100))

exposure_vector <- c("exposure","exposure2")
exposure_title <- c("Pesticide","Apple")

for (i in 1:length(exposure_vector)) {
  current_exposure <- db[[exposure_vector[i]]]
  title <- exposure_title[i]
  graph_name <- paste0(title,"_","Graph")
  p <- ggplot(db,aes(x=current_exposure,y=outcome))+
      geom_smooth()+
      theme_bw()+
      ylab("outcome")+
      xlab("exposure")+
      ggtitle(title)
  
  assign(graph_name, p)
  print(p)
}

ls()

##> [1] "Apple_Graph"      "current_exposure" "db"               "exposure_title"  
##> [5] "exposure_vector"  "graph_name"       "i"                "p"               
##> [9] "Pesticide_Graph"  "title"

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