Change color filling and position of legend in heatmap (gglot)

Question

Im trying to make a heatmap, that illustrates how intense a newspaper write about 30 different news topics over a timeperiod. The news topics can be grouped into 6 "meta topics" illustrated by the 6 different colors in the diagram below. However, I would like to fill out the color in each box of the upper legend, so it is easier to see (right now the color is only encircling each of the categories in the legend.) Secondly, I would like to change the location of the upper legend such that it is above the diagram. I have tried to add "theme(legend.position="top") + " to the code, but it doesn't change anything.

My code is:

all.data %>%
  dplyr::mutate(TopicName = fct_reorder(TopicName, metanumber)) %>%
  ggplot(aes(x = date, y = TopicName, color=MetaTopic,fill = rel_impact)) + geom_tile() +
  scale_x_date(date_breaks = "1 year", date_labels = "%Y",expand = c(0,0)) +
  scale_y_discrete(expand=c(0,0)) +
  theme(legend.position="bottom") +
  scale_colour_brewer(palette = "Dark2", name=NULL) +
  scale_fill_gradient(low = "white",high = "black", name=NULL) +
  labs(x=NULL, y="News topic") +
  theme_light(base_size = 11) 

Update: To reproduce the structure of the data, see the following code:

structure(list(SeriesID = c("Topic_1", "Topic_2", "Topic_1", "Topic_2", "Topic_1", "Topic_2"), date = structure(c(14760, 14760,  14790, 14790, 14821, 14821), class = "Date"), TopicName = c("Sport","Soccer", "Sport", "Soccer", "Sport", "Soccer"),MetaTopic = c("Sport", "Sport", "Sport", "Sport", "Sport", "Sport"),abs_impact = c(0.00169196071242834, 0.00237226605899713, 0.00031583852881164, 0.00096867233821691, 0.00020904777100742, 0.00023139444960141), sum = c(0.196227808854163, 0.196227808854163,0.047504294243804, 0.047504294243804,0.0296850112874241, 0.0296850112874241),rel_impact = c(0.00862243084865617,0.01208934693227, 0.00664863111512987,0.0203912583827778, 0.00704219947849513, 0.00779499281172378), metanumber = c(1, 1, 1, 1, 1, 1)), row.names= c(NA, -6L), class = c("tbl_df", "tbl", "data.frame"))

Hope you can help me out.

Answer 1

Edit: Moving legends independently

I arbitrarily changed some of the labels in the MetaTopic variable to make the change to your plot more apparent.

You can override the fill aesthetic used in the color legend, without affecting the other legend and mapping. I made palette to match your color scale, named my_palette in the example. Then I added guide(color = guide_legend(override.aes = list(fill = my_palette))) to your plot, to fill the color legend.

For your plot you'll want to change the number of colors in the palette to match the number of MetaTopics (3 in my example). Also note I increased the linewidth of the geom_tiles just for easy visibility in this example. You can remove that to revert to the default.

Moving legends independently takes a few more steps. First we create the plot with the legend in the default position on the right. Next, the legend is isolated using cowplot::get_legend with the color aesthetic's legend removed (its being added elsewhere). Finally, we assemble the plot in two parts: adding our fill override and position changes to a plot without the fill legend, and adding back the fill legend we extracted in the previous step. rel_widths sets the relative width of each column, with the fill legend being the 2nd column in this case.

library(tidyverse)
library(cowplot)

all.data <- structure(list(SeriesID = c("Topic_1", "Topic_2", "Topic_1", "Topic_2", "Topic_1", "Topic_2"), date = structure(c(14760, 14760,  14790, 14790, 14821, 14821), class = "Date"), TopicName = c("Sport","Soccer", "Sport", "Soccer", "Sport", "Soccer"),MetaTopic = c("Sport", "Leisure", "Sport", "Career", "Career", "Sport"),abs_impact = c(0.00169196071242834, 0.00237226605899713, 0.00031583852881164, 0.00096867233821691, 0.00020904777100742, 0.00023139444960141), sum = c(0.196227808854163, 0.196227808854163,0.047504294243804, 0.047504294243804,0.0296850112874241, 0.0296850112874241),rel_impact = c(0.00862243084865617,0.01208934693227, 0.00664863111512987,0.0203912583827778, 0.00704219947849513, 0.00779499281172378), metanumber = c(1, 1, 1, 1, 1, 1)), row.names= c(NA, -6L), class = c("tbl_df", "tbl", "data.frame"))

my_palette <- RColorBrewer::brewer.pal(3, 'Dark2')

# base plot
p1 <- all.data %>%
  dplyr::mutate(TopicName = fct_reorder(TopicName, metanumber)) %>%
  ggplot(aes(x = date, y = TopicName, color=MetaTopic,fill = rel_impact)) + 
  geom_tile(linewidth = 1) +
  scale_x_date(date_breaks = "1 year", date_labels = "%Y",expand = c(0,0)) +
  scale_y_discrete(expand=c(0,0)) +
  theme(legend.position="bottom") +
  scale_colour_brewer(palette = "Dark2", name=NULL) +
  scale_fill_gradient(low = "white",high = "black", name=NULL) +
  labs(x=NULL, y="News topic") +
  theme_light(base_size = 11)

# grab fill legend
guide_color <- get_legend(p1 + guides(color = 'none'))

# construct plot
plot_grid(p1 +
            guides(fill = 'none',
                   color = guide_legend(
                     override.aes = list(fill = my_palette))) +
            theme(legend.position = 'top'),
          guide_color,
          ncol = 2,
          rel_widths = c(0.9, 0.1)
          )

^{Created on 2023-05-02 with reprex v2.0.2}