如何固定ggplot连续色彩范围

Question

我无法根据其值固定热图的颜色。相同的值应具有相同的颜色。目标是将所有值保持在一定的阈值（0.05）以下（恒定）为灰色。对于大于此阈值的值，颜色应逐渐从“ firebrick1”更改为“ firebrick4”。

例如，如果使用变量utilization2，“ Plant 5” /“ 202004” = 70.6为红色，如果使用变量utilization，则为灰色。我该如何解决？

library(tidyverse)
library(rlang)

MONTHS <- str_c("2020", sprintf("%02d", 1:12))
PLANTS <- str_c("Plant ", 1:5)

crossing(month = MONTHS, plant = PLANTS) %>%
  mutate(utilization = runif(nrow(.), 70, 100)) %>%
  mutate(utilization2 = if_else(plant == "Plant 2", utilization * 0.67, utilization)) -> d

draw_plot <- function(fill) {
  fill <- ensym(fill)
   d %>%
    ggplot(mapping = aes(x = month, y = plant, fill = !!fill)) +
    geom_tile(aes(width = 0.85, height = 0.85)) +
    geom_text(aes(label = round(!!fill, 1)), color = "white") +
    scale_x_discrete(expand=c(0,0)) +
    scale_y_discrete(expand=c(0,0)) +
    scale_fill_gradientn(colours = c("darkgray", "firebrick1", "firebrick4"), 
                         values = c(0, 0.05, 1)) +
    labs(x = "Month", y = "Production plant", title = str_c("fill = ", fill), color = "Utilization") +
    theme_light() +
    theme(legend.position = "none")
}
draw_plot(utilization)
draw_plot(utilization2)

Answer 1

library(tidyverse)
library(rlang)

MONTHS <- str_c("2020", sprintf("%02d", 1:12))
PLANTS <- str_c("Plant ", 1:5)

crossing(month = MONTHS, plant = PLANTS) %>%
    mutate(utilization = runif(nrow(.), 70, 100)) %>%
    mutate(utilization2 = if_else(plant == "Plant 2", utilization * 0.67, utilization)) -> d

draw_plot <- function(fill) {
    fill <- ensym(fill)
    d %>%
        ggplot(mapping = aes(x = month, y = plant, fill = !!fill)) +
        geom_tile(aes(width = 0.85, height = 0.85)) +
        geom_text(aes(label = round(!!fill, 1)), color = "white") +
        scale_x_discrete(expand=c(0,0)) +
        scale_y_discrete(expand=c(0,0)) +
        scale_fill_gradientn(colours = c("darkgray", "firebrick1", "firebrick4"),
                             values = c(0, 0.05, 1), limits = c(min(d$utilization, d$utilization2), max(d$utilization, d$utilization2))) +
        labs(x = "Month", y = "Production plant", title = str_c("fill = ", fill), color = "Utilization") +
        scale_color_identity() +
        theme_light() +
        theme(legend.position = "none")
}
draw_plot(utilization)
draw_plot(utilization2)

关键是scale_fill_gradientn()将比例尺的极限设置为目标矢量的最大值和最小值。您必须手动设置它们。在这种情况下，我同时选择了两列的最大值和最小值（limits = c(min(d$utilization, d$utilization2), max(d$utilization, d$utilization2))）。

Answer 2

颜色在值之间插入，因此，您可以做的一个技巧是将0和0.05都设置为灰色，然后以很小的增量将下一个颜色设置为0.05。

draw_plot <- function(fill) {
  fill <- ensym(fill)
  d %>%
    ggplot(mapping = aes(x = month, y = plant, fill = !!fill)) +
    geom_tile(aes(width = 0.85, height = 0.85)) +
    geom_text(aes(label = round(!!fill, 1)), color = "white") +
    scale_x_discrete(expand=c(0,0)) +
    scale_y_discrete(expand=c(0,0)) +
    scale_fill_gradientn(colours = c("darkgray", "darkgray", "firebrick1", "firebrick4"), 
                         values = c(0, 0.05, 0.05 + .Machine$double.eps, 1)) +
    labs(x = "Month", y = "Production plant", title = str_c("fill = ", fill), color = "Utilization") +
    theme_light() +
    theme(legend.position = "none")
}
draw_plot(utilization)
draw_plot(utilization2)

也许不必提及，但是填充比例会根据限制将所有填充值重新调整为0-1之间的范围（请参见?scales::rescale），因此您在0.05参数中输入的values为utilization中范围值的底部5％，而不是未缩放的数据值，该值低于0.05。如果要在多个图上具有一致的填充比例，则必须手动设置limits参数。