Using mutate to swap columns renders a negative Difference output - gtsummary

Question

I have used the gtsummary package (great package btw) since last month on my reports.
Now I am building a cohort table that will show pre-test value, post-test value, difference (p.p) and a t-test p-value.
I'm trying to build the same table as I have built it under Arsenal with pre-test being the first column and post-test being in the second column and so on, but the difference column shows a negative output when it isn't supposed to be.
I used mutate() to swap both columns, as when I don't use it it shows the post-test as the first column. I also tried swapping the post-test columns at first rows in the dataset itself as what I read in some posts. But to no avail.
homesurvey %>%
select(period, CB2.Textbooks, CB2.Magazines, CB2.Newspapers, CB2.Religious_books, CB2.Coloring_books, CB2.Comics) %>%
mutate(period = forcats::fct_rev(period)) %>%
tbl_summary(by = period,
statistic = all_continuous() ~ "{n} ({sd})",
label = list (CB2.Textbooks ~ "Textbooks",
CB2.Magazines ~ "Magazines",
CB2.Newspapers ~ "Newspapers",
CB2.Religious_books ~ "Religious books",
CB2.Coloring_books ~ "Coloring books",
CB2.Comics ~ "Comics")
)%>%
add_difference() %>%
modify_column_hide(ci)
It shows a negative difference even if it isn't supposed to be.
Output

Answer 1

I am looking at your example output (thanks for including it). The first row is showing 82% in pre-assessment and 96% in the post-assessment. 82 - 96 = -15%, so the difference should indeed be negative.
You can, however, flip the estimate by multiplying it by -1. Example below!
library(gtsummary)
packageVersion("gtsummary")
#> [1] '1.5.0'
tbl <-
trial %>%
select(response, death, trt) %>%
tbl_summary(by = trt, missing = "no") %>%
add_difference() %>%
modify_column_hide(ci) %>%
# you can flip the difference estimate by multiplying it by -1
modify_table_body(
~.x %>%
dplyr::mutate(estimate = -1 * estimate)
)
Created on 2021-11-10 by the reprex package (v2.0.1)