How to plot conditional colored outlines of barplots according to some variable?

I have the following data

structure(list(date = structure(c(1L, 1L, 2L, 2L, 3L, 3L, 4L, 
4L, 5L, 5L, 6L, 6L, 7L, 7L, 8L, 8L, 9L, 9L, 10L, 10L), .Label = c("2011", 
"2012", "2013", "2014", "2015", "2016", "2017", "2018", "2019", 
"2020"), class = c("ordered", "factor")), station = c("41B001", 
"41B011_41R012", "41B001", "41B011_41R012", "41B001", "41B011_41R012", 
"41B001", "41B011_41R012", "41B001", "41B011_41R012", "41B001", 
"41B011_41R012", "41B001", "41B011_41R012", "41B001", "41B011_41R012", 
"41B001", "41B011_41R012", "41B001", "41B011_41R012"), concentration = c(NA, 
26.7276362390038, NA, 25.6793849658314, NA, 26.4231406374957, 
NA, 22.318982275586, NA, 22.0774877184965, NA, 21.6359649122807, 
56.1669215086646, 21.6140621430203, 56.1504197761194, 19.7031357486815, 
51.5015359168242, 17.0787333944114, 36.3595993515516, 11.4634841061866
), yield = c(0, 99.9200913242009, 0, 99.9544626593807, 0, 99.9200913242009, 
0, 99.8287671232877, 0, 99.9200913242009, 6.65983606557377, 99.931693989071, 
89.5890410958904, 99.9315068493151, 97.8995433789954, 99.5662100456621, 
96.62100456621, 99.6803652968037, 98.3151183970856, 99.9203096539162
), environ = structure(c(2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 
1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L), .Label = c("Urbain avec très faible influence du trafic", 
"Urbain avec très forte influence du trafic"), class = "factor"), 
    environ_station = structure(c(2L, 1L, 2L, 1L, 2L, 1L, 2L, 
    1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L), .Label = c("Urbain avec très faible influence du trafic (41B011, 41R012)", 
    "Urbain avec très forte influence du trafic (41B001)"), class = "factor")), row.names = c(NA, 
-20L), class = c("tbl_df", "tbl", "data.frame"))

It is plotted with the following code

ggplot(data, aes(x = date, y = concentration, fill = environ_station)) +
  geom_col(width = 0.75, colour = ifelse(round(data$yield, 0) < 85, "red", "black"), size = 0.5, position = position_dodge2(preserve = "single")) + guides(fill = guide_legend(nrow = 2)) +
  geom_hline(aes(yintercept = 40), linetype = 'dashed', colour = 'red', size = 1) +
  labs(x = '', y = label_conc) +
  theme_minimal() + theme(legend.position="bottom", legend.title = element_blank(), legend.margin=margin(l = -2, unit='line'),
                          legend.text = element_text(size = 10),
                          axis.text.y = element_text(size = 10), axis.title.y = element_text(size = 10), 
                          axis.text.x = element_text(size = 10), axis.title.x = element_blank(),
                          panel.grid.major.x = element_blank()) + geom_hline(yintercept = 0)

as this figure

However, the resulting outlines of the bars up to 2016 are drawn in red, while they are expected to be black since their yield is above 85. It seems that missing bars (with concentration = NA) from the second class is causing the issue (order mixup).

Any idea on how to fix this, please ? Thanks.

Solution

The issue is that you set the border colors via the color argument. To solve your issue set the color conditionally inside aes() and make use of scale_color_manual as I did in my approach below or make use of scale_color_identity.

Note: I dropped the resulting color legend via guides.

library(ggplot2)

ggplot(data, aes(x = date, y = concentration, fill = environ_station)) +
  geom_col(aes(colour = ifelse(round(yield, 0) < 85, "red", "black")), width = 0.75, 
           size = 0.5, position = position_dodge2(preserve = "single")) + 
  scale_color_manual(values = c(red = "red", black = "black")) +
  guides(fill = guide_legend(nrow = 2), color = FALSE) +
  geom_hline(aes(yintercept = 40), linetype = 'dashed', colour = 'red', size = 1) +
  #labs(x = '', y = label_conc) +
  theme_minimal() + theme(legend.position="bottom", legend.title = element_blank(), legend.margin=margin(l = -2, unit='line'),
                          legend.text = element_text(size = 10),
                          axis.text.y = element_text(size = 10), axis.title.y = element_text(size = 10), 
                          axis.text.x = element_text(size = 10), axis.title.x = element_blank(),
                          panel.grid.major.x = element_blank()) + geom_hline(yintercept = 0)
#> Warning: Removed 6 rows containing missing values (geom_col).