looping r-package "seg" function -with changing data selection - r

Question

I am calculating the dissimilarity index of several groups compared to the total population with the function "seg" from the identically named package.
The data consists of about 450 rows, each a different district, and around 20 columns (groups that may be segregated). The values are the number of people from respective group living in respective district. Here are the first few rows of my csv file:
Region,Germany,EU15 without Germany,Poland,Former Yugoslavia and successor countries,Former Soviet Union and successor countries,Turkey,Arabic states,West Afrika,Central Afrika,East Afrika,North America,Central America and the Carribean,South America,East and Central Asia,South and Southeast Asia - excluding Vietnam,Australia and Oceania,EU,Vietnam,Non EU Europe,Total Population
1011101,1370,372,108,35,345,91,256,18,6,3,73,36,68,272,98,3,1979,19,437,3445
1011102,117,21,6,0,0,0,6,0,0,0,7,0,6,0,7,0,156,0,3,188
1011103,2180,482,181,102,385,326,358,48,12,12,73,24,75,175,129,12,3152,34,795,5159
Since the seg function only works with two columns as input, my current code to create a table with the index for all groups looks like this:
DI_table <- as.data.frame(0)
DI_table[1,1] <- print (seg(data =dfplrcountrygroups2019[, c( "Germany", "Total.Population")]))
DI_table[1,2] <- print (seg(data =dfplrcountrygroups2019[, c( colnames(dfplrcountrygroups2019)[3], "Total.Population")]))
DI_table[1,3] <- print (seg(data =dfplrcountrygroups2019[, c( colnames(dfplrcountrygroups2019)[4], "Total.Population")]))
DI_table[1,4] <- print (seg(data =dfplrcountrygroups2019[, c( colnames(dfplrcountrygroups2019)[5], "Total.Population")]))
# and so on...
colnames(DI_table)<- (colnames(dfplrcountrygroups2019[2:20]))
Works well, but a hassle to recode every time I change something with my data and I would like to use this method for other datasets too.
I thought I might try something like below but the seg function did not consider it a selection of two columns.
for (i in colnames(dfplrcountrygroups2019)) {
di_matrix [i] <- seg(data =dfplrcountrygroups2019[, c( "i", "Total.Population")])
}
Error in [.data.frame(dfplrcountrygroups2019, , c("i",
"Total.Population")) : undefined columns selected
I also thought of the apply function but not sure how to make it work so it repeats itself while just changing the column where "Germany" is in the example. How do I make the selection of columns change for each time I repeat the seg function?
my_function <- seg(data =dfplrcountrygroups2019[, c("Germany", "Total.Population")])
apply(X = dfplrcountrygroups2019,
FUN = my_function,
MARGIN = 2
)
Error in get(as.character(FUN), mode = "function", envir = envir) :
object 'my_function' of mode 'function' was not found

Answer 1

The seg package's functions such as dissim (seg::seg is being deprecated in its favor) have a specific expected data format. From the docs:
data - a numeric matrix or data frame with two columns that represent mutually exclusive population groups (e.g., Asians and non-Asians). If more than two columns are given, only the first two will be used for computing the index.
To get a data frame of the d values seg::dissim returns, where each column is a region's dissimilarity index, you can iterate over the columns, making a temporary data frame and calculating the index. Because the data you're starting with isn't made up of mutually-exclusive categories, you'll have to subtract each population from the total population column to get a not-X counterpart for each group X.
A base R option with sapply will return a named list, which you can then convert into a data frame.
di_table <- sapply(names(dat)[2:20], function(col) {
tmp_df <- dat[col]
tmp_df$other <- dat$Total.Population - dat[col]
seg::dissim(data = tmp_df)$d
}, simplify = FALSE)
as.data.frame(di_table)
#> Germany EU15.without.Germany Poland
#> 1 0.03127565 0.03989693 0.02770549
#> Former.Yugoslavia.and.successor.countries
#> 1 0.160239
#> Former.Soviet.Union.and.successor.countries Turkey Arabic.states West.Afrika
#> 1 0.08808277 0.2047 0.02266828 0.1415519
#> Central.Afrika East.Afrika North.America Central.America.and.the.Carribean
#> 1 0.08004711 0.213581 0.1116014 0.2095969
#> South.America East.and.Central.Asia
#> 1 0.08486598 0.2282734
#> South.and.Southeast.Asia...excluding.Vietnam Australia.and.Oceania EU
#> 1 0.0364721 0.213581 0.04394527
#> Vietnam Non.EU.Europe
#> 1 0.05505789 0.06624686
A couple tidyverse options: you can use purrr functions to do something like above in one step.
dat[2:20] %>%
purrr::map(~data.frame(value = ., other = dat$Total.Population - .)) %>%
purrr::map_dfc(~seg::dissim(data = .)$d)
# same output
Or with reshaping the data and splitting by county. This takes more steps, but might fit a larger workflow better.
library(dplyr)
dat %>%
tidyr::pivot_longer(c(-Region, -Total.Population)) %>%
mutate(other = Total.Population - value) %>%
split(.$name) %>%
purrr::map_dfc(~seg::dissim(data = .[c("value", "other")])$d)
# same output