Using dtable or collect to add a column to a table containing the difference between two other columns

[David Hoehle]

Hello everyone,

I'm new to working with the commands dtable and collect, and I was wondering, if there was a way to add a column containing the difference of two other columns.

To be more specific, I look at the shares of the total population in comparison to a subgroup as in the example below. In the next step, I want to calculate the differences in the percentages for every row. Is there a way to do this?

clear all
sysuse auto, clear

// generating second factor variable
generate consumption = 0
replace consumption = 1 if mpg > 21

dtable i.foreign, by(consumption) sample(, statistic(frequency percent))         ///
    sformat("%s" percent fvpercent)


* put each statistic in a unique column
collect composite define column1 = frequency fvfrequency
collect composite define column2 = percent fvpercent
collect style autolevels result column1 column2, clear

collect query autolevels consumption
* reset the autolevels of the -by()- variable, putting .m;
collect style autolevels consumption .m `s(levels)', clear


collect style cell var[i.foreign], ///
    border(, width(1)) font(, size(7))
collect label levels consumption 0 "Lower" 1 "Higher"


collect layout (var[i.foreign]) (consumption[.m 1]#result)