Question

具有列ID，列类别，列成本和列颜色的数据框。

这是数据帧df

library(dplyr)

id <- c(1, 1, 1, 2, 2, 3, 1) 
category <- (c("V", "V", "V", "W", "W", "W", "W"))
cost <- c(10, 15, 5, 2, 14, 20, 3)
colour <- c("red", "green", "red", "green", "blue","blue","blue")

df <- data.frame(id, category, cost, colour)
df$category <- as.character(df$category)

df
id    category    cost     colour
1     V           10       red
1     V           15       green
1     V           5        red
2     W           2        green
2     W           14       blue
3     W           20       blue
1     W           3        blue

这是df的格式

'data.frame':   7 obs. of  4 variables:
 $ id       : num  1 1 1 2 2 3 1
 $ category : chr  "V" "V" "V" "W" ...
 $ cost: num  10 15 5 2 14 20 3
 $ colour   : Factor w/ 3 levels "blue","green",..: 3 2 3 2 1 1 1

我想要一个新的数据帧df_new，并为每个id提供频率（freq），条目等于W（category_W）的类别条目数，条目等于V的类别条目数（category_V ），类别条目为W（cost_W）的每个id的总成本，类别条目为V（cost_V）的每个id的总成本，以及每个唯一ID的每个颜色条目的数量（col_red，col_green，col_blue））。输出应该看起来像

id freq category_W    category_V    cost_W  cost_V    col_red  col_green col_blue
1  4      1             3             3       30        2           1       1     
2  2      2                          16                             1       1 
3  1      1                          20                                     1

我尝试了以下方法 - 但它没有效果。

df_new <- group_by(df, id) %>% summarize(freq = count(id), category_W = count(category == "W", na.rm=TRUE), category_V = count(category == "V", na.rm=TRUE), col_red = count(colour == "red", na.rm=TRUE), col_green = count(colour == "green", na.rm=TRUE),  col_blue = count(colour == "blue", na.rm=TRUE))

我不知道如何插入cost_W和cost_V的条件。我收到错误：length（rows）== 1不为TRUE 非常感谢提前！

Answer 1

嗯，你快到了。

您可以利用逻辑值在算术运算中转换为0和1的事实。因此，当您对它们求和时，您将获得逻辑子句测试的特定值的计数。

您可以使用相同的属性来计算成本。只需将逻辑子句与成本变量相乘即可。如果类别与您的兴趣匹配，则将其相加，否则，将其减少为0

df_new <-
    group_by(df, id) %>% summarize(
      freq = n(),
      category_W = sum(category == "W", na.rm = TRUE),
      category_V = sum(category == "V", na.rm = TRUE),
      cost_W = sum((category == "W") * cost, na.rm = TRUE),
      cost_V = sum((category == "V") * cost, na.rm = TRUE),
      col_red = sum(colour == "red", na.rm = TRUE),
      col_green = sum(colour == "green", na.rm = TRUE),
      col_blue = sum(colour == "blue", na.rm = TRUE)
  )

如何使用dplyr聚合数据帧的多个列

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