R 如何向量化过滤器 table 查找

Question

我正在寻找一种方法来矢量化 table 查找。这是我预期 input/output 不使用循环的示例。

library(dplyr)
library(tidyr)


input <- tibble(
  value = c(2, 1.5, 3), 
  color = c('blue', 'green', NA)
)
table_lookup <- tibble(
  min = c(0.5, 1.5, 2.5), 
  max = c(1.5, 2.5, 99999), 
  color = c('green', 'blue', NA), 
  output = c(8:10)
 )
## Desired output By filtering "value" from the input between min (excluded min) and max and color match with color from "table_lookup".
c(9, 8, 10)

谢谢，

约翰

Answer 1

我们可以将 sapply 与 which 函数一起使用：

sapply(input$value, 
       FUN = function(x) table_lookup$output[which(x > table_lookup$min & x <= table_lookup$max)])

另一种选择是使用 merge 然后 filter:

merge(input, table_lookup, by = NULL) %>%
    filter(value > min, value <= max)

#   value color.x min     max color.y output
# 1   1.5   green 0.5     1.5   green      8
# 2   2.0    blue 1.5     2.5    blue      9
# 3   3.0    <NA> 2.5 99999.0    <NA>     10

Answer 2

您可以使用：

library(fuzzyjoin)
fuzzy_left_join(x = input, 
                y = table_lookup, 
                by = c("value" = "min", "value" = "max"), 
                match_fun = list(`>`, `<=`))

# A tibble: 3 x 6
  value color.x   min     max color.y output
  <dbl> <chr>   <dbl>   <dbl> <chr>    <int>
1   2   blue      1.5     2.5 blue         9
2   1.5 green     0.5     1.5 green        8
3   3   NA        2.5 99999   NA          10

R 如何向量化过滤器 table 查找

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