Creating loop for plotting in ggplot2 leads to error

Question

this has been posted before in a similar style, but I have adjusted a few things now and hopefully (!) things are clear now

I've tried to create a loop in order to create plots for several countries.

My dataframe: Plot_df

Here an excerpt of the data:

year country iso2      sector emissions
1990 Belgium   BE         ETS         0
1990 Belgium   BE   Regulated  78614107
1990 Belgium   BE Unregulated  41870292
1991 Belgium   BE         ETS         0
1991 Belgium   BE   Regulated  79811521
1991 Belgium   BE Unregulated  43733190
...
2011 Belgium   BE         ETS  46203056
2011 Belgium   BE   Regulated  61319344
2011 Belgium   BE Unregulated  42839297
2012 Belgium   BE         ETS  43006980
2012 Belgium   BE   Regulated  58934979
2012 Belgium   BE Unregulated  42459997
2013 Belgium   BE         ETS  45231176
2013 Belgium   BE   Regulated  58383554
2013 Belgium   BE Unregulated  43586891
2014 Belgium   BE         ETS  43853144
2014 Belgium   BE   Regulated  56010346
2014 Belgium   BE Unregulated  40380694
2015 Belgium   BE         ETS  44713916
2015 Belgium   BE   Regulated  57375031
2015 Belgium   BE Unregulated  42854461
2016 Belgium   BE         ETS  43655728
2016 Belgium   BE   Regulated  56702848
2016 Belgium   BE Unregulated  43540863

dput(head(Plot_df, 15)) delivers this

structure(list(year = c("1990", "1990", "1990", "1990", "1990", 
"1990", "1990", "1990", "1990", "1990", "1990", "1990", "1990", 
"1990", "1990"), country = c("Austria", "Austria", "Austria", 
"Belgium", "Belgium", "Belgium", "Bulgaria", "Bulgaria", "Bulgaria", 
"Croatia", "Croatia", "Croatia", "Cyprus", "Cyprus", "Cyprus"
), iso2 = c("AT", "AT", "AT", "BE", "BE", "BE", "BG", "BG", "BG", 
"HR", "HR", "HR", "CY", "CY", "CY"), sector = c("ETS", "Regulated", 
"Unregulated", "ETS", "Regulated", "Unregulated", "ETS", "Regulated", 
"Unregulated", "ETS", "Regulated", "Unregulated", "ETS", "Regulated", 
"Unregulated"), emissions = c(0, 38264402.6689529, 24027827.7997971, 
0, 78614106.9221497, 41870291.5153503, 0, 69103153.6445618,         
9569791.66793823, 
0, 17530229.1374207, 5911735.70632935, 0, 3135556.17528036, 1507499.48878214
)), row.names = c("378", "2836", "3100", "813", "8310", "8410", 
"558", "16410", "16510", "438", "24510", "24610", "783", "3261", 
"3271"), class = "data.frame")

I have only shown the whole data for one country, since every country looks the same (apart from different figures Plot_df$emissions )

What I want to do is (most you will see from my code below):

• create loop, so plots will be created for all countries
• x axis = year; y=emissions (of a country as in Plot_df$country )
• 3 groups (curves) should be from `Plot_df$sector: Regulated, Unregulated, ETS Regulated and unregulated should be between 1990:2016; ETS between 2005:2017. (these years are the years with data availability)

This is what I tried:

# Sets up the loop to run from i=1 through a list of countries from vector 
`Plot_df$country`
for(i in (1:length(unique(Plot_df$country)))){

# Color settings: colorblind-friendly palette
cols <- c("#999999", "#E69F00", "#56B4E9", "#009E73", "#F0E442", "#0072B2", 
        "#D55E00", "#CC79A7")

# Plotting code where DATA, YEAR, etc need to be handed the right vectors
p <- ggplot() +
geom_line(Plot_df,aes(x=year,y=emissions,group=sector),
          color=cols[1]) +
labs(x="Year",y="CO2 emissions",z="",title=paste("Emissions for", 
country[i])) + 
xlim(1990, 2016) +
ylim(-50,50) +
theme(plot.margin=unit(c(.5,.5,.5,.5),"cm"))
p

# Save plot, where the file name automatically gets a country name suffix
 ggsave(p,filename=paste("./FILENAME",country[i],".png",sep=""),width=6.5, 
     height=6)
}

I'm getting this error and I can't figure out why

Error: `data` must be a data frame, or other object coercible by 
`fortify()`, not an S3 object with class uneval
Did you accidentally pass `aes()` to the `data` argument?

Any idea why this is happening?

Thanks in any case

Answer 1

FWIW a teensy bit of code styling goes a long way.

for(country in unique(Plot_df$country)) {

  # YOU NEVER *REALLY* USE THIS VECTOR JUST ONE ELEMENT FROM IT

  # Color settings: colorblind-friendly palette
  c(
    "#999999", "#E69F00", "#56B4E9", "#009E73", 
    "#F0E442", "#0072B2", "#D55E00", "#CC79A7"
  ) -> cols

  # carve out the data for the plot
  country_df <- Plot_df[Plot_df$country == country,]

  # Plotting code where DATA, YEAR, etc need to be handed the right vectors
  ggplot() +
    geom_line(
      data = country_df, # THIS IS WHAT YOU FORGOT
      aes(year, emissions, group = sector), 
      color = cols[1] # WHY [1] IF YOU DEFINED A VECTOR
    ) +
    xlim(1990, 2016) + # SHOULD LIKELY USE scale_x_… and set limits there + expand=c(0,0) insteasd
    ylim(-50, 50) + # SAME
    labs(
      x = "Year", y = "CO2 emissions", 
      title = sprintf("Emissions for %s", country)
    ) + 
    theme(plot.margin = margin(.5, .5, .5, .5, "cm")) -> p # THERE IS A margin() function

  print(p) # it won't print without print()

  # Save plot, where the file name automatically gets a country name suffix
  ggsave(
    plot = p, 
    filename = sprintf("./FILENAME-%s.png", country), # I PREFER sprintf
    width = 6.5, 
    height = 6
  )
}