R 数据转换：根据不同列中的数字创建新行

Question

I am searching for a solution how to transform the following data frame using dplyr:

item <- c('A','B','C')
one <- c(2, 1, 2)
two <- c(1,1,2)
data <- data.frame(item,one,two)
data

item	one	two
A	2	1
B	1	1
C	2	2

Now, the column "one" contains the number of ratings of the value 1, the column "two" the number of ratings of the value 2. My ideal data frame after transformation would look like this:

item	rating
A	1
A	1
A	2
B	1
B	2
C	1
C	1
C	2
C	2

Any idea how I could get to this output (it doesn't have to be dplyr)? I know how to use pivot_longer of the tidyr package but that doesn't solve the problem of repeating the number of rows...

Answer 1

library(dplyr)
library(tidyr) # pivot_longer
nums <- c(one = 1, two = 2, three = 3)
data %>%
  pivot_longer(-item) %>%
  group_by(item) %>%
  summarize(rating = rep(name, times = value)) %>%
  ungroup() %>%
  mutate(rating = nums[rating])
# # A tibble: 9 x 2
#   item  rating
#   <chr>  <dbl>
# 1 A          1
# 2 A          1
# 3 A          2
# 4 B          1
# 5 B          2
# 6 C          1
# 7 C          1
# 8 C          2
# 9 C          2

I had to define nums because I couldn't find (in my haste) an easy way to convert "one" to 1 in a programmatic way. You'll need to make sure it goes out at least as far as you need; I added three=3 for demonstration, if you truly only have one and two then you should be good as-is.

(Related to that topic: Convert written number to number in R )

Answer 2

也许您可以使用gather()函数将其从宽格式转换为长格式，然后将“一”和“二”的字符串值替换为整数