Plot multiple dataframes with a loop/function

Question

I have 18 dataframes named chr1, chr2 ... chr18.

And the following (simplified) code to produce a plot:

p1 <- ggplot(chr1, aes(V4, colour = factor(V6)))+ 
  geom_freqpoly(binwidth=1, size=0.8) +
  labs(x="score", y="Number of Mutations", title = "Chromosome 1") +
  theme_bw()

My idea is a function that would:

Create plot object with an increasing number (p1, p2 .. p${chr})
Taking the data from different dataframes (chr1, chr2 .. chr${chr})
And would also change the title name according to the chromosome (title = "Chromosome ${chr})

I believe I once had similar code that used a list of dataframes, but I can't remember how it worked.

Thanks

tamarack · Accepted Answer · 2022-06-28 20:10:20Z

This is not a function, but creates the individual plot objects:

library(ggplot2)

chr.list <- list(
  chr1 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr2 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr3 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr4 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr5 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T))
)

for (i in 1:length(chr.list)) {
  assign(x = paste0('p', i),
         value = ggplot(chr.list[[i]], aes(V4, colour = factor(V6))) +
           geom_freqpoly(binwidth = 1, size = 0.8) +
           labs(x = 'score', y = 'Number of Mutations', title = paste('Chromosome', i)) + 
           theme_bw()
        )
}

assign() takes a character string and creates an object with that name. For example: assign(x = 'x', value = 2) creates a variable, x, with a value of 2.

########

This is a function that returns a list of the plot objects, and the names of the list elements are p1, p2, p3, etc

library(ggplot2)

chr.list <- list(
  chr1 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr2 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr3 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr4 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr5 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T))
)


plot.chrs <- function(chr.list) {
  ## create an empty list with the same length as chr.list
  plot.list <- vector(mode = 'list', length = length(chr.list))
  
  for (i in 1:length(chr.list)) {
    plot.list[[i]] <- ggplot(chr.list[[i]], aes(V4, colour = factor(V6))) +
                       geom_freqpoly(binwidth = 1, size = 0.8) +
                       labs(x = 'score', y = 'Number of Mutations', 
                            title = paste('Chromosome', i)) + 
                       theme_bw()
    names(plot.list)[i] <- paste0('p', i)
  }
  
  return(plot.list)
}

########

This is a function that creates the plots as individual objects in your global environment:

library(ggplot2)

chr.list <- list(
  chr1 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr2 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr3 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr4 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T)),
  chr5 = data.frame(V4 = sample(1:100, 20), V6 = sample(1:3, 20, replace = T))
)


plot.chrs <- function(chr.list) {
  plot.list <- vector(mode = 'list', length = length(chr.list))
  
  for (i in 1:length(chr.list)) {
    plot.list[[i]] <- ggplot(chr.list[[i]], aes(V4, colour = factor(V6))) +
                       geom_freqpoly(binwidth = 1, size = 0.8) +
                       labs(x = 'score', y = 'Number of Mutations', 
                            title = paste('Chromosome', i)) + 
                       theme_bw()
    names(plot.list)[i] <- paste0('p', i)
  }
  
  return(plot.list)
}

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