library(tidyverse)
library(plotly)

# I'm being lazy, please don't do this
# setwd("~/Downloads/Version 2_0_1/")

d <- read_csv('GEOSTAT_grid_POP_1K_2011_V2_0_1.csv') %>%
  rbind(read_csv('JRC-GHSL_AIT-grid-POP_1K_2011.csv') %>%
          mutate(TOT_P_CON_DT = '')) %>%
  mutate(
    lat = as.numeric(gsub('.*N([0-9]+)[EW].*', '\\1', GRD_ID))/100,
    lng = as.numeric(gsub('.*[EW]([0-9]+)', '\\1', GRD_ID)) * ifelse(gsub('.*([EW]).*', '\\1', GRD_ID) == 'W', -1, 1) / 100
  ) %>%
  filter(lng > 25, lng < 60) %>%
  group_by(lat = round(lat, 1), lng = round(lng, 1)) %>%
  summarize(value = sum(TOT_P, na.rm = T))  %>%
  ungroup() %>%
  tidyr::complete(lat, lng)

p <- ggplot(d, aes(lng, lat + 5*(value / max(value, na.rm = T)))) +
  geom_line(
    aes(group = lat, text = paste("Population:", value)),
    size = 0.4, alpha = 0.8, color = '#5A3E37', na.rm = T
  ) +
  ggthemes::theme_map()

# support for coord_equal() coming soon! For now, you can do this...
ggplotly(p, tooltip = "text") %>%
  layout(xaxis = list(scaleanchor = "y", scaleratio = 0.9))