How can I create a new column based on conditional statements and dplyr?

问题

I have four conditions

maxx = 3, minx = 1, maxy = 6, miny = 3. (If minx < x < maxx and miny < y < maxy, then z = apple)
maxx = 6, minx = 4, maxy = 9, miny = 7. (If minx < x < maxx and miny < y < maxy, then z = ball)
maxx = 2, minx = 0, maxy = 5, miny = 3. (If minx < x < maxx and miny < y < maxy, then z = pine)
maxx = 12, minx = 7, maxy = 15, miny = 11. (If minx < x < maxx and miny < y < maxy, then z = orange)

Expected outcome:

x y z
2 4 apple
5 8 ball
1 4 pine 
9 12 orange

I have thousands of rows, and these four conditions that will fit all values.

How can I do this using the mutate function? I know how to manipulate numbers directly, but not sure how I can store a character based on conditional statements.

回答1:

Alternative answer:

library(mosaic)
df <- mutate(df, fruit = derivedFactor(
  "apple" = (x<3 & x>1 & y<6 & y>3),
  "ball" = (x<6 & x>4 & y<9 & y>7),
  "pine" = (x<2 & x>0 & y<5 & y>3),
  "orange" = (x<12 & x>7 & y<15 & y>11),
   method ="first",
  .default = NA
))

回答2:

I believe the best option here is to use dplyr::case_when

df %>% mutate(z = case_when(
    x < 3  & x > 1 & y < 6  & y > 3  ~ "apple" ,
    x < 6  & x > 4 & y < 9  & y > 7  ~ "ball"  ,
    x < 2  & x > 0 & y < 5  & y > 3  ~ "pine"  ,
    x < 12 & x > 7 & y < 15 & y > 11 ~ "orange"
  )
)

Which gives us:

# A tibble: 4 x 3
      x     y z     
  <dbl> <dbl> <chr> 
1     2     4 apple 
2     5     8 ball  
3     1     4 pine  
4     9    12 orange

回答3:

Using ifelse, it's

df %>% mutate(z = ifelse(x<3 & x>1 & y<6 & y>3, 'apple', 
                         ifelse(x<6 & x>4 & y<9 & y>7, 'ball',
                                ifelse(x<2 & x>0 & y<5 & y>3, 'pine',
                                       ifelse(x<12 & x>7 & y<15 & y>11, 'orange', NA))))
)

#   x  y      z
# 1 2  4  apple
# 2 5  8   ball
# 3 1  4   pine
# 4 9 12 orange

Notes:

If you have cases that match two conditions (x = 1.5, y = 4), this will fail.
dplyr also has a between helper function that can reduce your conditions to two calls each, but it uses <= and >=, so you'd need to reconfigure your endpoints.
You could use switch, but all your conditions would need to be in the first term, which will end up looking exactly like the ifelse version, and your cases will have nothing to do.
If your ranges don't overlap, this is better solved with cut, which is easy to implement for one variable and could be overwritten by a second.

来源：https://stackoverflow.com/questions/36003699/how-can-i-create-a-new-column-based-on-conditional-statements-and-dplyr

标签

dplyr