Add # of units discarded in bal.tab()$Observations when using subclassification with discard

[sky0502]

Hi, I have a suggestion to add # of units discarded in bal.tab()$Observations when using subclassification with discard. For example,

library(MatchIt)
library(cobalt)
data("lalonde")
m_out <- matchit(treat ~ age + educ + race + married + nodegree, 
                 data = lalonde, method = "subclass", distance = "glm", discard = "both")
m_summary <- bal.tab(m_out)
m_summary$Observations

Currently it returns

          1  2  3  4  5  6 All
Control 297 21 24 15  9 14 429
Treated  31 31 30 31 31 30 185
Total   328 52 54 46 40 44 614

Add a column of "discarded" so that the numbers add up to "All".

          1  2  3  4  5  6 Discarded All
Control 297 21 24 15  9 14       49  429
Treated  31 31 30 31 31 30        1  185
Total   328 52 54 46 40 44       50  614

[ngreifer]

Great suggestion, thanks!