Count specific characters from column associated with dual categories of other column. Do it iteratively based on frequency bins

问题

I have a huge dataframe df1, whose oversimplified version consists of 3 columns, "Words", "Frequency" and "Letters":

Words           Frequency   Letters
flower/tree     0.15        a(0.1)
tree            0.67        a(0.4)
planet          0.85        b(0.4)
tree/planet     0.42        c(0.5)
tree            0.89        a(0.6)
flower          0.21        b(0.4)
flower/planet   0.53        b
planet          0.07        a

Using R (dplyr, apply family functions, etc.) I would like to count the number of times every letter (a, b, c) of the "Letter" column is associated with every single word from the "Word" column (flower, tree, planet), in an iterative way dependent on the frequency bin of the "Frequency" column values. There are 4 bins: [0, 0.25], [0.25, 0.5], [0.5, 0.75], [0.75, 1].

I expect an output dataframe df2 that looks something like this:

Bin       Word    Letters    count_letters
0-0.25    flower  a          1
0-0.25    flower  b          1
0-0.25    tree    a          1
0-0.25    planet  a          1
0.25-0.5  tree    c          1
0.25-0.5  planet  c          1
0.5-0.75  flower  b          1
0.5-0.75  tree    a          1
0.5-0.75  planet  b          1
0.75-1    tree    a          1
0.75-1    planet  b          1

回答1:

You can use cut to bin Frequency, substr to clean Letters, and tidyr::separate_rows to unnest Word. Aggregate with dplyr::count, and you're set:

library(tidyverse)

df %>% separate_rows(Words) %>% 
    count(Words, 
          Letters = substr(Letters, 1, 1),    # use regex if more than one letter
          Frequency = cut(Frequency, breaks = seq(0, 1, .25)))

## Source: local data frame [11 x 4]
## Groups: Frequency, Words [?]
## 
##     Frequency  Words Letters     n
##        <fctr>  <chr>   <chr> <int>
## 1    (0,0.25] flower       a     1
## 2    (0,0.25] flower       b     1
## 3    (0,0.25] planet       a     1
## 4    (0,0.25]   tree       a     1
## 5  (0.25,0.5] planet       c     1
## 6  (0.25,0.5]   tree       c     1
## 7  (0.5,0.75] flower       b     1
## 8  (0.5,0.75] planet       b     1
## 9  (0.5,0.75]   tree       a     1
## 10   (0.75,1] planet       b     1
## 11   (0.75,1]   tree       a     1

来源：https://stackoverflow.com/questions/42237800/count-specific-characters-from-column-associated-with-dual-categories-of-other-c

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dataframe

dplyr

apply