R/plotRot.R

In cbw1243/cdlRotate: Access Cropland Data Layer Data and Analyze Land Use Changes in the United States

#' Generate land use transition data for area of interest.
#'
#' A function that generate land use transitions from year1 to year2 for area of interest.
#'
#' @param data Land use change data generated by the \code{rotate} function.
#' @param top  Top land use types.
#'
#' @return
#' The function returns a ggplot object.
#'
#' @export
#'
#'
plotRot <- function(data, top = 5){
  data <- as.data.frame(data)

  topuse <- dplyr::filter(data, value.x != 0, value.y != 0)
  topuse <- dplyr::group_by(topuse, value.x)
  topuse <- dplyr::summarise(topuse, counts = sum(counts))
  topuse <- dplyr::arrange(topuse, dplyr::desc(counts))

  fsuse <- topuse$value.x[1:top]

  datasub <- dplyr::filter(data, value.x %in% fsuse, value.y %in% fsuse)
  datasub <- dplyr::mutate(datasub, value.x = as.character(value.x),
                                    value.y := as.character(value.y))

  g <-
    ggplot2::ggplot(datasub, ggplot2::aes(value.y, value.x, fill= counts)) +
    ggplot2::geom_tile() +
    viridis::scale_fill_viridis(discrete=FALSE) +
    ggplot2::labs(x = 'Land use category in year 2', y = 'Land use category in year 1') +
    ggplot2::coord_fixed() +
    ggplot2::theme_minimal() +
    ggplot2::theme(axis.text = ggplot2::element_text(colour = 'black'),
          legend.position = 'right')

  return(g)
}