CODEWITHSUNDEEP
rdplyr
hacketju
hacketju

Reputation: 25

R/Plyr function for outputting column value based on the maximum value in another column, by group

I have a data frame with three columns (Mouse, Day, vol). I am trying to use dplyr to create a new dataframe to extract the last "Day" value for each mouse and the corresponding "vol" for that mouse. I am able to use the max function to get the right "Day" but am having trouble grabbing the matching "vol". Any help is appreciated. Below is my dataframe dput and the code I am trying to assemble.

final_meas <- ddply(df, "Mouse", summarise,
               final_day = max(Day),
               final_vol = 
)

If there is a better way to do this please let me know.

Data frame dput()

structure(list(Mouse = c("CF1", "CF2", "CG1", "CG2", "CG3", "CO1", 
"CO2", "CU1", "CY1", "CF1", "CF2", "CG1", "CG2", "CG3", "CO1", 
"CO2", "CU1", "CY1", "CF1", "CF2", "CG1", "CG2", "CG3", "CO1", 
"CO2", "CU1", "CY1", "CF1", "CF2", "CG1", "CG2", "CG3", "CO1", 
"CO2", "CF2", "CG1", "CG2", "CG3", "CO1", "CF2", "CG1", "CG2", 
"CG3", "CO1", "CF2", "CG1", "CG2", "CG3", "CO1", "CF2", "CG1", 
"CG2", "CG3", "CO1", "CF2", "CG1", "CG2", "CG3", "CO1", "CF2", 
"CG1", "CG2", "CG3", "CO1"), Day = c(11, 11, 11, 11, 11, 11, 
11, 11, 11, 14, 14, 14, 14, 14, 14, 14, 14, 14, 16, 16, 16, 16, 
16, 16, 16, 16, 16, 21, 21, 21, 21, 21, 21, 21, 26, 26, 26, 26, 
26, 28, 28, 28, 28, 28, 30, 30, 30, 30, 30, 32, 32, 32, 32, 32, 
35, 35, 35, 35, 35, 38, 38, 38, 38, 38), vol = c(45.9675, 36.1712655, 
87.777976, 14.29754, 14.2842745, 22.989735, 19.3821875, 56.216752, 
71.251488, 0.5, 44.6299425, 119.070536, 26.82875, 21.999132, 
71.801216, 0.5, 255.874619, 137.720968, 0.5, 21.5552, 115.16616, 
33.132848, 17.619264, 51.185368, 0.5, 212.1728, 340.5686, 0, 
0.5, 75.154122, 76.0952875, 0.5, 107.208528, 0, 0.5, 63.5839875, 
233.4784, 0.5, 74.6727445, 0.5, 55.7932375, 361.3029455, 0, 88.297668, 
0.5, 38.0849105, 228.4934, 0.5, 136.778328, 0.5, 0.5, 186.7279545, 
0.5, 178.4032435, 0.5, 0, 186.7279545, 0.5, 89.4645, 0.5, 0, 
186.7279545, 0.5, 169.296399)), row.names = c(NA, -64L), class = c("tbl_df", 
"tbl", "data.frame"))

Upvotes: 0

Views: 23

Answers (1)

Bruno
Bruno

Reputation: 4151

Here is one approach using the tidyverse

library(tidyverse)

df_example %>% 
  group_by(Mouse) %>% 
  mutate(max_day = max(Day),
         max_vol = if_else(Day == max(Day),vol,NA_real_)) %>% 
  fill(max_vol,.direction = "downup")

Upvotes: 1

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