Plot doesn't show negative values - r

Question

I am doing the map of the world showing profit and loss from different countries.
I already plotted the map, I prepared and joined data, Im at the final step.
My dataset is 'data_profit', 'Total_profit' are values Im using (negative and positive ones)- and it's used to fill the map with colors, depending on the value.
Rest of the code is map plotting.
ditch_the_axes <- theme(
axis.text = element_blank(),
axis.line = element_blank(),
axis.ticks = element_blank(),
panel.border = element_blank(),
panel.grid = element_blank(),
axis.title = element_blank()
)
terra<-ggplot(data_profit, aes( x = long, y = lat, group = group )) +
geom_polygon(aes(x = long, y = lat,fill = Total_profit),color = "black")+
coord_fixed(1.3) +
theme_bw() +
ditch_the_axes+
scale_fill_gradient2( low="black", high="red", space ="Lab" )
data_profit <-
structure(list(long = c(-69.8991241455078, -69.8957061767578,
-69.9421920776367, -70.004150390625, -70.0661163330078, -70.0508804321289
), lat = c(12.4520015716553, 12.4229984283447, 12.4385251998901,
12.50048828125, 12.5469722747803, 12.5970697402954), group = c(1,
1, 1, 1, 1, 1), order = 1:6, region = c("Aruba", "Aruba", "Aruba",
"Aruba", "Aruba", "Aruba"), Total_profit = c(0, 0, 0, 0, 0, 0
)), row.names = c(NA, 6L), class = "data.frame")
and this is the output map:
So, the thing is the final map doesn't show the negative values (which should be in shade of black and grey). I checked whether 'Total_profit' values are numeric (with is.finite and is.numeric).
Do you have any idea what to change in the code?

Answer 1

Your question is unfortunately not reproducible, so I created some different sample data. I also suggest using "world map" and geom_map instead of geom_polygon (see below).
I assume the problem in your plot is a combination of missing values and the lack of correct limits in scale_..._gradient. Using scale_...gradientn comes with another problem - the asymmetric midpoint. (see here)
library(tidyverse)
library(scales) #load this for the mid-point problem and using scales::rescale (see below)
WorldData <- map_data('world') #easier way to draw countries than using geom_polygon
# In the next steps I am merging your profit data with the world map. I am creating a different sample data frame
data_profit <- data.frame(region = sample(WorldData$region,6), Total_profit = c(-5, -3, 0, 3, 5, 10))
map_profit <- dplyr::left_join(WorldData, data_profit, by ='region')
#> Warning: Column `region` joining character vector and factor, coercing into
#> character vector
# This plot is the easier one - using scale_fill_gradient(...). No mid-point problem. Note I am specifying the NA color using na.value.
# I am also specifying the limits using limits = ... I am not hard coding this, giving more flexibility for future graphs.
ggplot() +
geom_map(data = map_profit, map = WorldData,
aes(x = long, y = lat, map_id = region, fill = Total_profit, na.rm = FALSE)) +
scale_fill_gradient(low="black", high="red", na.value = 'blue',
limits = c(min(map_profit$Total_profit), max(map_profit$Total_profit)))
#> Warning: Ignoring unknown aesthetics: x, y, na.rm
# The next plot comes with the problem of an asymmetric mid-point
# I therefore rescale the values using rescale
ggplot() +
geom_map(data = map_profit, map = WorldData,
aes(x = long, y = lat, map_id = region, fill = Total_profit, na.rm = FALSE)) +
scale_fill_gradientn(colors = c("black", 'white', "red"), na.value = 'blue',
values = rescale(c(min(map_profit$Total_profit, na.rm = TRUE),0, max(map_profit$Total_profit,na.rm = TRUE))),
limits = c(min(map_profit$Total_profit), max(map_profit$Total_profit)))
#> Warning: Ignoring unknown aesthetics: x, y, na.rm
Created on 2019-07-11 by the reprex package (v0.3.0)