Question

我需要使用名为df的数据框在ggplot2中绘制线形图，

   DATE       ITEM        NUMBER_SOLD
    <date>     <chr>       <int>
 1 2018-01-08 APPLE         3
 2 2018-01-09 APPLE         3
 3 2018-01-09 PEAR          2
 4 2018-01-09 ORANGE        1
 5 2018-01-10 APPLE         2
 6 2018-01-10 PEAR          1
 7 2018-01-12 CHERRY        2
 8 2018-01-12 MANGO         1
 9 2018-01-15 PINEAPPLE     1
10 2018-01-15 APRICOT       1

等

数据框基本上是一个小标题，显示特定商品在2018年的某一天售出了336行。

该图必须是显示某项特定商品（苹果）的销售的折线图，其日期在x轴上，售出的数量在y轴上，另外一行在y轴上，表明销售额增加了15％像这样：

df %>% filter(ITEM == "APPLE") %>%
  ggplot(aes(DATE, NUMBER_SOLD)) +
  geom_line(size = 1, col = "red") +
  theme(axis.text.x = element_text(angle = 90)) +
  geom_line(aes(y = NUMBER_SOLD + NUMBER_SOLD/100*15), col = "green4", size = 1, alpha = 0.6) +
  scale_x_date(date_labels="%b", date_breaks  = "1 month")

但是，我还需要添加一个图例以显示两条线所代表的内容，例如红色线代表原始销售数量，绿色线代表原始销售数量+ 15％。我该如何实现？

Answer 1

诀窍是先在数据框中进行计算，然后使用gather()将数据转为长整数，然后将数字放入一列，并用另一个变量指示每个数字是用于实际销售还是预期销售。

library(tidyverse)

df <- tribble(~"DATE",       ~"ITEM",        ~"NUMBER_SOLD",
"2018-01-08", "APPLE",         3,
"2018-01-09", "APPLE",         3,
"2018-01-09", "PEAR",          2,
"2018-01-09", "ORANGE",        1,
"2018-01-10", "APPLE",         2,
"2018-01-10", "PEAR",          1,
"2018-01-12", "CHERRY",        2,
"2018-01-12", "MANGO",         1,
"2018-01-15", "PINEAPPLE",     1,
"2018-01-15", "APRICOT",       1) %>% 
  mutate(DATE = parse_date(DATE),
         NUMBER_SOLD_EXP = NUMBER_SOLD + NUMBER_SOLD/100*15) %>% 
  gather(key = category, value = SOLD, NUMBER_SOLD, NUMBER_SOLD_EXP)

df
# A tibble: 20 x 4
   DATE       ITEM      category         SOLD
   <date>     <chr>     <chr>           <dbl>
 1 2018-01-08 APPLE     NUMBER_SOLD      3   
 2 2018-01-09 APPLE     NUMBER_SOLD      3   
 3 2018-01-09 PEAR      NUMBER_SOLD      2   
 4 2018-01-09 ORANGE    NUMBER_SOLD      1   
 5 2018-01-10 APPLE     NUMBER_SOLD      2   
 6 2018-01-10 PEAR      NUMBER_SOLD      1   
 7 2018-01-12 CHERRY    NUMBER_SOLD      2   
 8 2018-01-12 MANGO     NUMBER_SOLD      1   
 9 2018-01-15 PINEAPPLE NUMBER_SOLD      1   
10 2018-01-15 APRICOT   NUMBER_SOLD      1   
11 2018-01-08 APPLE     NUMBER_SOLD_EXP  3.45
12 2018-01-09 APPLE     NUMBER_SOLD_EXP  3.45
13 2018-01-09 PEAR      NUMBER_SOLD_EXP  2.3 
14 2018-01-09 ORANGE    NUMBER_SOLD_EXP  1.15
15 2018-01-10 APPLE     NUMBER_SOLD_EXP  2.3 
16 2018-01-10 PEAR      NUMBER_SOLD_EXP  1.15
17 2018-01-12 CHERRY    NUMBER_SOLD_EXP  2.3 
18 2018-01-12 MANGO     NUMBER_SOLD_EXP  1.15
19 2018-01-15 PINEAPPLE NUMBER_SOLD_EXP  1.15
20 2018-01-15 APRICOT   NUMBER_SOLD_EXP  1.15

现在，您只需要调用一次geom_line，使用变量上的color参数指示该数字是实际出售还是预期出售。您需要添加scale_colour_manual()来指定要附加到类别的颜色。

df %>% filter(ITEM == "APPLE") %>%
  ggplot(aes(DATE, SOLD)) +
  geom_line(aes(colour = category), size = 1) +
  scale_colour_manual(values = c("NUMBER_SOLD" = "red", "NUMBER_SOLD_EXP" = "green")) +
  theme(axis.text.x = element_text(angle = 90)) +
  scale_x_date(date_labels="%b", date_breaks  = "1 month")

如何在ggplot2中为多层添加自定义图例？

1 个答案: