Save ggplot in loop with R

Question

I have a dataset with numeric and factor variables. I want to do one page with numeric and other with factor var. First of all, i select factor var with his index.

My df is IRIS dataset.

df<-iris
df$y<-sample(0:1,nrow(iris),replace=TRUE)
fact<-colnames(df)[sapply(df,is.factor)]
index_fact<-which(names(df)%in%fact)

Then i calculate rest of it (numerics)

nm<-ncol(df)-length(fact)

Next step is create loop

i_F=1
i_N=1
list_plotN<- list()
list_plotF<- list()

for (i in 1:length(df)){
  plot <- ggplot(df,aes(x=df[,i],color=y,fill=y))+xlab(names(df)[i]) 

  if (is.factor(df[,i])){
    p_factor<-plot+geom_bar()
    list_plotF[[i_F]]<-p_factor
    i_F=i_F+1
  }else{
    p_numeric <- plot+geom_histogram()
    list_plotN[[i_N]]<-p_numeric
    i_N=i_N+1
  }
}

When i see list_plotF and list_plot_N,it didn't well. It always have same vars. i don't know what i'm doing wrong.

thanks!!!

I cannot see any value for y in your example

Andrea
– Andrea

2019-01-15 17:47:59 +00:00
Commented Jan 15, 2019 at 17:47 — Andrea
– Andrea, Commented Jan 15, 2019 at 17:47
This might help stackoverflow.com/a/50383146/786542

Tung
– Tung

2019-01-15 18:02:45 +00:00
Commented Jan 15, 2019 at 18:02 — Tung
– Tung, Commented Jan 15, 2019 at 18:02

Sahir Moosvi · Accepted Answer · 2019-01-15 19:33:04Z

1

I don't really follow your for loop code all that well. But from what I see it seems to be saving the last plot in every loop you make. I've reconstructed what I think you need using lapply. I generally prefer lapply to for loops whenever I can.

Lapply takes a list of values and a function and applies that function to every value. you can define your function separately like I have so everything looks cleaner. Then you just mention the function in the lapply command.

In our case the list is a list of columns from your dataframe df. The function it applies first creates our base plot. Then it does a quick check to see if the column it is looking at is a factor.. If it's a factor it creates a bar graph, else it creates a histogram.

histOrBar <- function(var) {
  basePlot <- ggplot(df, aes_string(var))
  if ( is.factor(df[[var]]) ) {
    basePlot + geom_bar()  
  } else {
    basePlot + geom_histogram()
  }
}

loDFs <- lapply(colnames(df), histOrBar)

answered Jan 15, 2019 at 19:33

Sahir Moosvi

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2 Comments

liguang Over a year ago

is there possible to pass df like argument of apply? @Sahir Moosvi

Sahir Moosvi Over a year ago

There is a set of apply functions. the base apply function can take a dataframe.

Parfait · Accepted Answer · 2019-01-16 16:09:13Z

1

Consider passing column names with aes_string to better align x with df:

for (i in 1:length(df)){
    plot <- ggplot(df, aes_string(x=names(df)[i], color="y", fill="y")) + 
              xlab(names(df)[i]) 
    ...
}

To demonstrate the problem using aes() and solution using aes_string() in OP's context, consider the following random data frame with columns of different data types: factor, char, int, num, bool, date.

Data

library(ggplot2)

set.seed(1152019)
alpha <- c(LETTERS, letters, c(0:9))
data_tools <- c("sas", "stata", "spss", "python", "r", "julia")

random_df <- data.frame(
  group = sample(data_tools, 500, replace=TRUE),
  int = as.numeric(sample(1:15, 500, replace=TRUE)),
  num = rnorm(500),
  char = replicate(500, paste(sample(LETTERS[1:2], 3, replace=TRUE), collapse="")),
  bool = as.numeric(sample(c(TRUE, FALSE), 500, replace=TRUE)),
  date = as.Date(sample(as.integer(as.Date('2019-01-01', origin='1970-01-01')):as.integer(Sys.Date()), 
                        500, replace=TRUE), origin='1970-01-01')
)

Graph

fact <- colnames(random_df)[sapply(random_df,is.factor)]
index_fact <- which(names(random_df) %in% fact)

i_F=1
i_N=1
list_plotN <- list()
list_plotF <- list()
plot <- NULL

for (i in 1:length(random_df)){
  # aes() VERSION
  #plot <- ggplot(random_df, aes(x=random_df[,i], color=group, fill=group)) +
  #  xlab(names(random_df)[i]) 

  # aes_string() VERSION
  plot <- ggplot(random_df, aes_string(x=names(random_df)[i], color="group", fill="group")) +
    xlab(names(random_df)[i]) 

  if (is.factor(random_df[,i])){
    p_factor <- plot + geom_bar()
    list_plotF[[i_F]] <- p_factor
    i_F=i_F+1
  }else{
    p_numeric <- plot + geom_histogram()
    list_plotN[[i_N]] <- p_numeric
    i_N=i_N+1
  }
}

Problem (using aes() where graph outputs DO NOT change according to type)

Solution (using aes_string() where graphs DO change according to type)

edited Jan 16, 2019 at 16:09

answered Jan 15, 2019 at 18:39

Parfait

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9 Comments

Parfait Over a year ago

Really? What error do you get? Works great on my end.

Parfait Over a year ago

Come to think of it, your problem is unclear. It always have same vars. ... what does this mean? Without aes_string, the x-axis does not change between plots which I assumed is your same vars issue.

liguang Over a year ago

If you see list_plotF (expected graphs for factor vars) and list_plotN (expected graphs numerical vars), you could check both list are same. even plot is a list with all plots.

Parfait Over a year ago

I edited showing the differences in using aes() and aes_string() in your context. I believe iris may not be a good example since all columns except species are numeric. See my random data (seeded for reproducibility) of columns of all types: char, num, int, bool, and date. See the problem and solution outputs.

Parfait Over a year ago

What IDE are you using? RStudio? RGui? Rscript at command line? How are you viewing the plots?

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