ggplot line chart helper function

helper.R

#### helper function for trajectory line chart:
#### note: there is global variable in this function!!!
helper_vis_continuous <- function(dat = country_data, country = 'US') {
  ## vertical structure for ggplot
  current_dat = dat %>%
    filter(Country.Region == country) %>%
    reshape2::melt(.) %>%
    set_colnames(c('Country', 'Status', 'Date', 'Total'))

  ## starts with the date when 1st case was confirmed for this country 
  case1_idx = which(current_dat$Total > 0)[1]
  current_dat = current_dat[case1_idx:nrow(current_dat), ]

  plot <-
    ggplot(dat = current_dat,
           aes_string(x = 'Date', y = 'Total', color = 'Status', group = 'Status', linetype = 'Status')) +
    geom_line(lwd = 1.2) +
    labs(subtitle = sprintf('%s', country)) +
    xlab('Date') + ylab('Total Numbers') +
    theme_bw() +
    theme(plot.title = element_text(hjust = 0.5),
          plot.subtitle = element_text(hjust = 0.5),
          axis.text.x = element_text(angle = 75, hjust = 1), 
          panel.grid.major = element_blank(),
          panel.grid.minor = element_blank(), 
          legend.position = 'None')
          
  return(plot)
}