Saving ggplot to a list then applying to grid.arrange geom_line from last plot populates all previous plots

Question

I am very new to R and ggplot2. I am trying to create a grid of plots of correlations as well as their trailing max and min values using a for loop. The plots are then saved as a PDF to a directory. When they are saved the blue lines(min max) are correctly plotted. However when I then use the do.call(grid.arrange,t) or any other call to the plots in the list. you do not get the correct blue lines, but the last plots blue lines populate all of the plots.

I dont understand how this can plot and save the pdf correctly but not store the ggplot object correctly in the t list() or how there is some confusion in the render using do.call(grid.arrange,t). How can the original line (black) plot correctly but the geom_line additions do not ? I am really confused.

If someone could kindly help me check this code and find out how to plot all lines correctly then place them in a grid that would be great.

reproducable code below using random data

require(TTR)
require(ggplot2)
library(gridExtra)

set.seed(12345)
filelocation = "c:/"
values <- as.data.frame(matrix( rnorm(5*500,mean=0,sd=3), 500, 5))

t <- list()
rollLength = 25
for( i in 1:(ncol(values)))
{
p <- ggplot(data=values, aes(x = index(values)) ) 
p <- p + geom_line(data=values, aes_string(y = colnames(values)[i]))
p <- p + geom_line(data = values, aes(x = index(values), y = runMax(values[,i], n = rollLength) ), colour = "blue", linetype = "longdash" )
p <- p + geom_line(data = values, aes(x = index(values), y = runMin(values[,i], n = rollLength) ), colour = "blue", linetype = "longdash" )
p <- p + ggtitle(colnames(values)[i]) + xlab("Date") + ylab("Pearson Correlation")
print(p)
ggsave( file = paste(colnames(values)[i],".pdf",sep = "") , path = filelocation)
assign(paste("p", i, sep = ""), p)
t[[i]] <- p
}

do.call(grid.arrange,t)

sckott sckott · Accepted Answer · 2013-10-31T04:31:14

Hmm, this isn't exactly what you want I think, but close, and less code

require(TTR)
require(ggplot2)

set.seed(12345)
values <- as.data.frame(matrix( rnorm(5*500,mean=0,sd=3), 500, 5))
rollLength = 25

library(reshape2)
dfmelt <- melt(values)
dfmelt$max <- runMax(dfmelt$value, n=rollLength)
dfmelt$min <- runMin(dfmelt$value, n=rollLength)
dfmelt$row <- index(dfmelt)
ggplot(dfmelt, aes(x = row, y = value)) +
  geom_line() +
  geom_line(aes(x = row, y = max), data=dfmelt, colour = "blue", 
                                   linetype = "longdash") +
  geom_line(aes(x = row, y = min), data=dfmelt, colour = "blue", 
                                   linetype = "longdash") +
  facet_wrap(~ variable, scales="free")

enter image description here

Saving ggplot to a list then applying to grid.arrange geom_line from last plot populates all previous plots

1 Answers