Can I use dplyr mutate to divide multiple rows against another row?

user_18121725 0
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I have the following test data:

df <- data.frame(group = c('Control' , 'Low' , 'Middle' , 'High') ,
                 type = c('A' , 'A' , 'A' , 'A') ,
                 value = c('3' , '5' , '2' , '4'))

I'm attempting to find each ratio for the values of "Low" , "Middle" , "High" against the value for "Control" - Low/Control, Middle/Control , High/Control.

I've trying this using mutate and ifelse, however, the function returns an NA.

df %>%
  group_by(group) |> 
  mutate(value = ifelse(group == 'Low' , value / value[Trt == 'Control'] , value))

I'd like to find a function that will return the appropriate result for each of the ratios.

dplyr r
1 Answers

The group_by seems to be 'type' column (based on the input data)

library(dplyr)
df <- df %>%
  type.convert(as.is = TRUE) %>%
  group_by(type) %>% 
  mutate(value1 = value/value[group == "Control"]) %>%
  ungroup

-output

df
# A tibble: 4 × 4
  group   type  value value1
  <chr>   <chr> <int>  <dbl>
1 Control A         3  1    
2 Low     A         5  1.67 
3 Middle  A         2  0.667
4 High    A         4  1.33
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