Only keep the characters in front of "_" per row in a single column then create a new colu-CodePudding

I have a large data frame called data_frame with two columns PRE and STATUS that look like this:

PRE         STATUS
1_752566    GAINED
1_776546    LOST
1_832918    NA
1_842013    LOST
1_846864    GAINED
11_8122943  NA
11_8188699  GAINED
11_8321128  NA
23_95137734 NA
23_95146814 GAINED

What I would like is to create a new column CHR with only the number(s) before the underscore and make sure they are matched up next to the original column correctly like this:

PRE         STATUS   CHR
1_752566    GAINED   1
1_776546    LOST     1
1_832918    NA       1
1_842013    LOST     1
1_846864    GAINED   1
11_8122943  NA       11
11_8188699  GAINED   11
11_8321128  NA       11
23_95137734 NA       23
23_95146814 GAINED   23

From here I'd like to group CHR by number and then find the sum of each group. If possible, I would like a new data table showing the sums of each group number like this:

NUM  SUM
1    5
11   3
23   2

I would then plot this to visualize the sums of each number where my x-axis is NUM and my y-axis is SUM

CodePudding user response：

We could extract the prefix before the _

library(dplyr)
df <- df %>%
      mutate(CHR = trimws(PRE, whitespace = "_.*"))

-output

df
           PRE STATUS CHR
1     1_752566 GAINED   1
2     1_776546   LOST   1
3     1_832918   <NA>   1
4     1_842013   LOST   1
5     1_846864 GAINED   1
6   11_8122943   <NA>  11
7   11_8188699 GAINED  11
8   11_8321128   <NA>  11
9  23_95137734   <NA>  23
10 23_95146814 GAINED  23

Then, based on the expected output showed, it will be the count we need

df %>%
 count(CHR, name = "SUM")
 CHR SUM
1   1   5
2  11   3
3  23   2

For the plot, do

library(ggplot2)
df %>%
  count(CHR, name = "SUM") %>%
  ggplot(aes(x = CHR, y = SUM))  
   geom_col()

data

df <- structure(list(PRE = c("1_752566", "1_776546", "1_832918", "1_842013", 
"1_846864", "11_8122943", "11_8188699", "11_8321128", "23_95137734", 
"23_95146814"), STATUS = c("GAINED", "LOST", NA, "LOST", "GAINED", 
NA, "GAINED", NA, NA, "GAINED")), class = "data.frame", row.names = c(NA, 
-10L))

CodePudding user response：

Here is an alternative approach using parse_number() from readr package:

parse_number will extract only the first numbers. Here only the number before _:

library(dplyr)
library(readr)
df %>% 
  group_by(CHR = parse_number(PRE)) %>% 
  summarise(NUM = first(CHR), SUM =n()) %>% 
  select(-CHR)

    NUM   SUM
  <dbl> <int>
1     1     5
2    11     3
3    23     2