Changing breaks on a geom_tile() heatmap

Question

I am working on the following dataframe:

structure(c(NA, 52, 22, 52, 111, 0, 3, 16, 5, 0, 0, 80, NA, 14, 
243, 14, 41, 1, 177, 3, 0, 20, 26, 8, NA, 13, 21, 10, 0, 0, 0, 
0, 0, 59, 29, 7, NA, 15, 20, 0, 8, 8, 0, 0, 111, 9, 273, 1733, 
NA, 60, 3, 14, 164, 0, 8, 20, 171, 53, 932, 135, NA, 0, 33, 3, 
0, 144, 21, 0, 3, 1, 2, 0, NA, 1, 0, 0, 0, 23, 81, 14, 146, 20, 
19, 5, NA, 1, 1, 0, 11, 4, 4, 8, 11, 0, 2, 12, NA, 0, 0, 1, 0, 
4, 32, 0, 16, 0, 3, 0, NA, 0, 0, 40, 2, 1, 0, 0, 0, 1, 5, 0, 
NA), .Dim = c(11L, 11L), .Dimnames = list(c("WILL_", "WOULD_", 
"MAY_", "MIGHT_", "CAN_", "COULD_", "SHALL_", "SHOULD_", "MUST_", 
"OUGHT TO_", "USED TO_"), c("_WILL", "_WOULD", "_MAY", "_MIGHT", 
"_CAN", "_COULD", "_SHALL", "_SHOULD", "_MUST", "_OUGHT TO", 
"_USED TO")))

And I have the following plot:

reshape2::melt(twitter_us_no_clit_matrix_nohave, value.name = "Freq") %>%
  mutate(label = ifelse(is.na(Freq) | Freq == 0, "", as.character(Freq))) %>%
  ggplot(aes(Var2, fct_rev(Var1))) +
  geom_tile(aes(fill = Freq), color = "black") +
  geom_text(aes(label = label), color = "black") +
  scale_fill_gradient(low = "grey", high = "purple", na.value = "black") +
  scale_x_discrete(NULL, expand = c(0, 0), position="top") +
  scale_y_discrete(NULL, expand = c(0, 0)) +
  theme(axis.text.x = element_text(angle=60,vjust = 0.5, hjust = 0))

It's all looking good but I'm trying to figure out how to change the breaks so that it changes the heatmap and its "Freq" label accordingly.

The breaks would be c(0,1,5,10,50,100,500,100000) and would make the values look more or less like the following in terms of colour heat:

Which exact lines should I tweak in my geom_tile()?

tlaus tlaus · Accepted Answer · 2021-01-21T14:38:52

If I understand correctly, you want to divide your continuous scale into steps. I had some success using the scale_fill_steps() function:

library(tidyverse)

twitter_us_no_clit_matrix_nohave <- structure(c(NA, 52, 22, 52, 111, 0, 3, 16, 5, 0, 0, 80, NA, 14, 
            243, 14, 41, 1, 177, 3, 0, 20, 26, 8, NA, 13, 21, 10, 0, 0, 0, 
            0, 0, 59, 29, 7, NA, 15, 20, 0, 8, 8, 0, 0, 111, 9, 273, 1733, 
            NA, 60, 3, 14, 164, 0, 8, 20, 171, 53, 932, 135, NA, 0, 33, 3, 
            0, 144, 21, 0, 3, 1, 2, 0, NA, 1, 0, 0, 0, 23, 81, 14, 146, 20, 
            19, 5, NA, 1, 1, 0, 11, 4, 4, 8, 11, 0, 2, 12, NA, 0, 0, 1, 0, 
            4, 32, 0, 16, 0, 3, 0, NA, 0, 0, 40, 2, 1, 0, 0, 0, 1, 5, 0, 
            NA), .Dim = c(11L, 11L), .Dimnames = list(c("WILL_", "WOULD_", 
                                                        "MAY_", "MIGHT_", "CAN_", "COULD_", "SHALL_", "SHOULD_", "MUST_", 
                                                        "OUGHT TO_", "USED TO_"), c("_WILL", "_WOULD", "_MAY", "_MIGHT", 
                                                                                    "_CAN", "_COULD", "_SHALL", "_SHOULD", "_MUST", "_OUGHT TO", 
                                                                                    "_USED TO")))

breaks <- c(0,1,5,10,50,100,500,100000)

reshape2::melt(twitter_us_no_clit_matrix_nohave, value.name = "Freq") %>%
  mutate(label = ifelse(is.na(Freq) | Freq == 0, "", as.character(Freq))) %>%
  ggplot(aes(Var2, fct_rev(Var1))) +
  geom_tile(aes(fill = Freq), color = "black") +
  geom_text(aes(label = label), color = "black") +
  scale_fill_steps(low = "grey", high = "purple", breaks = breaks, na.value = "black") + 
  scale_x_discrete(NULL, expand = c(0, 0), position="top") +
  scale_y_discrete(NULL, expand = c(0, 0)) +
  theme(axis.text.x = element_text(angle=60,vjust = 0.5, hjust = 0))

However, given the varying distance between your breaks, most of the scale is in gray. I don't know if you want to preserve that perspective.

For rescaling the colors, change the line to

scale_fill_steps(low = "grey", high = "purple", breaks = breaks, na.value = "grey", trans = "log")

which will make them evenly distributed in your scale. I was unsuccessful at setting them manually. I changed the color of the NA value, because now all your zeroes are NAs due to the log transformation.

Changing breaks on a geom_tile() heatmap

1 Answers