How can I apply a calculation to a dataframe when a value is not equal to a specified string?-CodePudding

Say I have the following table and only want to sum when the column does not contain "Fred". If the value does contain "Fred" I want to sum and multiply by 2. How can I achieve this preferably using dplyr?

Name  |  x   |  Expected Value |
Jack  |  15  |  17             |
Sally |  3   |  3              |
Fred  |  10  |  20             | 
Jack  |  2   |  17             |

Obviously this is not a serious table, but in essence, I just want to know how to apply a different basic calculation for a specified unique value in a large dataset.

CodePudding user response：

in Base R:

 transform(df, expect = ave((1   (Name == 'Fred')) * x, Name, FUN = sum))

   Name  x expect
1  Jack 15     17
2 Sally  3      3
3  Fred 10     20
4  Jack  2     17

Consider using tidyverse:

library(tidyverse)
df %>%
  group_by(Name) %>%
  mutate(expect = sum((1   (Name == 'Fred')) * x))

  Name      x expect
  <chr> <int>  <dbl>
1 Jack     15     17
2 Sally     3      3
3 Fred     10     20
4 Jack      2     17

CodePudding user response：

this is a a very simple way to solve your situation:

sample_table<- data.table(
Name = c('Jack','Sally','Fred','Jack'),
x = c(15,3,10,2),
exp = c(17,3,20,17))

sample_table[Name%in%"Fred",end_value:=(x exp)*2]

sample_table[!(Name%in%"Fred"),end_value:=(x exp)]