Add columns with 1-differences between values and 2-switchted values with conditions-CodePudding

I have a simple data frame:

dataframe_initial <- data.frame(
  Pot = c("1", "1", "2", "2", "3", "3"),
  Mass = c("25","37","51","42","34","29")
)

And I want this:

dataframe_wanted <- data.frame(
  Pot = c("1", "1", "2", "2", "3", "3"),
  Mass = c("25","37","51","42","34","29"),
  Mass_reverse = c("37","25","42","51","29","34"),
  Mass_diff = c("-12","12","9","-9","5","-5")
)

I apologize if this is quite obvious, but I took a long look on the web, without convincing help. To put it in words, I want to:

1-Add a new column with existing data (here mass), but reserved with conditions on a third column (Pot)

2- Add a new column with the differences between two values in the same initial column (Mass), but with conditions on a third column (Pot)

Many thanks in advance,

CodePudding user response：

Do a reverse after grouping and then get the difference (-)

library(dplyr)
dataframe_initial %>%  
  type.convert(as.is = TRUE) %>% # // automatically change the class
  group_by(Pot) %>% 
  mutate(Mass_reverse = rev(Mass),
         Mass_diff = Mass - Mass_reverse) %>% 
  ungroup

-output

# A tibble: 6 × 4
    Pot  Mass Mass_reverse Mass_diff
  <int> <int>        <int>     <int>
1     1    25           37       -12
2     1    37           25        12
3     2    51           42         9
4     2    42           51        -9
5     3    34           29         5
6     3    29           34        -5

NOTE: quoting the values make them character class.