Loop and save ggplot

Question

I have the following code that produces a graph. I want to loop around this code and input different values for the y = (which is currently XYZ). For each ggplot graph I want to save the output. For example first loop would be y = XYZ, second loop y = ABC, third loop y = QRS etc.

UK<-ggplot(Diff, aes(x = FactSet.Fund.Code  , y = XYZ, colour = Fund.Manager.x))
UK<- UK + geom_point(data = subset(Diff,DeskName.x=="UK Equities"), size = 6)
UK<- UK + theme(axis.text = element_text(angle = 90))

Maybe you need aes_string rather than aes, since you're looping. Saving plots depends on if you want separate png files or one pdf file with multiple pages. — Sean Lin
– Sean Lin, Commented Aug 22, 2017 at 15:31

Sean Lin · Accepted Answer · 2017-08-22 17:07:46Z

2

Usually ggplots are saved in a list, try below:

Y_list = c('XYZ', 'ABC', 'QRS')
g_list = list()
for (yi in Y_list) {
    UK<-ggplot(Diff, aes_string(x = 'FactSet.Fund.Code', y = yi, colour = 'Fund.Manager.x'))
    UK<- UK + geom_point(data = subset(Diff,DeskName.x=="UK Equities"), size = 6)
    UK<- UK + theme(axis.text = element_text(angle = 90))
    g_list[[yi]] = UK
}

edited Aug 22, 2017 at 17:07

answered Aug 22, 2017 at 15:42

Sean Lin

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2 Comments

user8491385 Over a year ago

Thanks, first solution looks good although I don't want to save the plot (my miscommunication!) I just want to assign it to an object. So just before the ggsave, the first loop would name the object with the plot as UKXYZ, the second loop would name is UKABC if you get me?

Sean Lin Over a year ago

@user8491385 I misunderstood you, please try updated answer.

be_green · Accepted Answer · 2017-08-22 15:39:02Z

This should work. Sean is totally right about aes_string making it work. aes normally uses something called non-standard evaluation (if you are unfamiliar, I'd recommend reading here). For your purposes, what it means is that you can't just pass i in the loop below directly to aes, because aes will interpret it as a column, instead of evaluating what information i contains. aes_string just lets you pass in the name of the column as a string. Then you can just save each plot off individually in your loop.

library(ggplot2)


code_list <- list("ABC","XYZ")

Diff <- data.frame(FactSet.Fund.Code = as.character(1:10), 
                   XYZ = rnorm(1:10), ABC = rnorm(1:10))

for(i in code_list){
   ggplot(Diff, aes_string(x = "FactSet.Fund.Code", y = i)) +
              geom_point(size = 6)
  ggsave(paste0(i,".png"))
}

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