R: Count number of rows in columns for a specific value, in a data subset

Question

I'm trying now for some days to find a solution to something really simple, with no luck. Here it is:

I've got a data frame with a row called RESPONSE.
I'm subsetting condition A and then grouping by Subject.
I'd like to count the sum of the cases per Subject where RESPONSE==44 and RESPONSE==77. However, not every subject has these, so for some subjects this sum should be 0.

I tried various commands, incl. summarise, count, filter. But I either get an aggregate of the cases overall for everyone, or it drops participants who don't have 77 or 44 (as opposed to assigning them a 0).

I imagine the code should look something like:

Condition_A <- subset(df, Condition=="A") %>%
  group_by(Subject) %>%
  sum(df$RESPONSE==77 | df$RESPONSE==44)

I see other people using sum the same way but I get an error that all my variables need to be numeric, and the row RESPONSE itself is. I'd be extremely grateful for any help here. Thank you.

Paul · Accepted Answer · 2020-11-06 16:44:58Z

1

Use summarise.

library(tidyverse)

df <- tribble(
  ~Condition, ~Subject, ~RESPONSE,
         "A",        1,        77,
         "A",        1,        44,
         "A",        1,         1,
         "A",        2,         1,
         "A",        2,         1,
         "A",        2,        44,
         "A",        3,         1
)

df %>%
  filter(Condition == "A") %>%
  group_by(Subject) %>%
  summarise(
    responses = sum(RESPONSE == 77 | RESPONSE == 44, na.rm = TRUE)
  )
#> # A tibble: 3 x 2
#>   Subject responses
#>     <dbl>     <int>
#> 1       1         2
#> 2       2         1
#> 3       3         0

edited Nov 6, 2020 at 16:44

answered Nov 6, 2020 at 16:39

Paul

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3 Comments

Orestes_Fox Over a year ago

Unfortunately, I did everything exactly the same and I still get only 1x1 output, with a single value, summarised for all my participants. For some reason it just would not group by Subject. Do you have any possible suggestion?

Paul Over a year ago

It sounds like the summarise function from plyr is being used instead of dplyr. Replace summarise with dplyr::summarise.

Orestes_Fox Over a year ago

Million thanks! That was exactly the problem! Have a lovely evening :))))

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