Override default colors in ggplot2

Question

This is probably an easy question for ggplot2 experts: I want to use my own colors rather than the default colors. How to achieve that?

Here's a snippet of the data:

df <- structure(list(start = c(0, 251, 1976, 5127, 5717, 6783), end = c(251, 
1976, 5127, 5717, 6783, 6830), minute = c(0L, 0L, 0L, 0L, 0L, 
0L), AOI = c("*", "A", "*", "*", "A", "*"), AOI_col = c("blue", 
"red", "blue", "blue", "red", "blue")), row.names = c(NA, -6L
), groups = structure(list(minute = 0L, .rows = structure(list(
    1:6), ptype = integer(0), class = c("vctrs_list_of", "vctrs_vctr", 
"list"))), row.names = 1L, class = c("tbl_df", "tbl", "data.frame"
), .drop = TRUE), class = c("grouped_df", "tbl_df", "tbl", "data.frame"
))

The colors I wish to plot are in column AOI_col. Here's the code so far:

library(ggplot2)
ggplot(df5, aes(x = start, xend = end, 
                y = minute + scale(as.numeric(as.factor(AOI)))/10,
                yend = minute + scale(as.numeric(as.factor(AOI)))/10,
                color = AOI)) +
  geom_segment(size = 2) +
  scale_y_reverse(breaks = 0:53, labels = paste0(0:53, "min"), name = NULL) +
  labs(title = "Gaze activity Speaker C F01") +
  theme(axis.title.x.bottom = element_blank())

I've tried using aes(fill = AOI_col) and scale_color_manual(values = AOI_col) but to no avail. Help is appreciated!

Answer 1

You can add a color adjustment in the geom_segment():

ggplot(df, aes(x = start, xend = end, 
                y = minute + scale(as.numeric(as.factor(AOI)))/10,
                yend = minute + scale(as.numeric(as.factor(AOI)))/10)) +
  geom_segment(size = 2, color = df$AOI_col) +
  scale_y_reverse(breaks = 0:53, labels = paste0(0:53, "min"), name = NULL) +
  labs(title = "Gaze activity Speaker C F01") +
  theme(axis.title.x.bottom = element_blank()) 

Or again the complete example with the answer from @user438383:

df <-
  structure(
    list(
      start = c(0, 251, 1976, 5127, 5717, 6783),
      end = c(251,
              1976, 5127, 5717, 6783, 6830),
      minute = c(0L, 0L, 0L, 0L, 0L,
                 0L),
      AOI = c("*", "A", "*", "*", "A", "*"),
      AOI_col = c("blue",
                  "red", "blue", "blue", "red", "blue")
    ),
    row.names = c(NA,-6L),
    groups = structure(
      list(
        minute = 0L,
        .rows = structure(
          list(1:6),
          ptype = integer(0),
          class = c("vctrs_list_of", "vctrs_vctr",
                    "list")
        )
      ),
      row.names = 1L,
      class = c("tbl_df", "tbl", "data.frame"),
      .drop = TRUE
    ),
    class = c("grouped_df", "tbl_df", "tbl", "data.frame")
  )

library(ggplot2)
ggplot(df,
       aes(
         x = start,
         xend = end,
         y = minute + scale(as.numeric(as.factor(AOI))) / 10,
         yend = minute + scale(as.numeric(as.factor(AOI))) / 10,
         color = AOI
       )) +
  geom_segment(size = 2) +
  scale_y_reverse(breaks = 0:53,
                  labels = paste0(0:53, "min"),
                  name = NULL) +
  labs(title = "Gaze activity Speaker C F01") +
  theme(axis.title.x.bottom = element_blank()) +
  scale_colour_manual(values = unique(df$AOI_col))

Answer 2

I think the ideal thing to do is make AOI_col a factor and sort it alphabetically, then assign the colours to be the unique values of that column:

df5$AOI_col = factor(df5$AOI_col, levels = sort(unique(df$AOI_col)))

ggplot(df5, aes(x = start, xend = end, 
                y = minute + scale(as.numeric(as.factor(AOI)))/10,
                yend = minute + scale(as.numeric(as.factor(AOI)))/10,
                color = AOI)) +
  geom_segment(size = 2) +
  scale_y_reverse(breaks = 0:53, labels = paste0(0:53, "min"), name = NULL) +
  labs(title = "Gaze activity Speaker C F01") +
  theme(axis.title.x.bottom = element_blank()) +
  scale_colour_manual(values = unique(df$AOI_col))