长 ifelse 语句的替代方案

Question

Say I have three individuals and I know the payment they require to enter different amounts of land into a scheme. I want to know how much land each participant would enter into the scheme for a given payment rate. I want them to enter the max amount they are willing for that payment rate. Previously I did this with a long ifelse statement, but that will not run inside a loop, so I'm looking for an alternative.

In this example, I've excluded a load of areas so it just presents as if participants can enter 50, 49 or 1 unit(s) of area.

paym_sh1a=200
paym_area_50 <- c(250, 150, 210)
paym_area_49 <- c(240, 130, 190)
paym_area_1 <- c(100, 20, 90)

 area_enrolled<- 
   ifelse(paym_area_50<paym_sh1a,50,ifelse(paym_area_49<paym_sh1a,49, 
 ifelse(paym_area_1<paym_sh1a,1,0)))

Answer 1

You could create a table of your values:

paym_area = rbind(paym_area_50, paym_area_49, paym_area_1)

And then use vectorised operations more effectively. In particular, since your thresholds are decreasing, you could compare the whole table to the sh1a value, and count how many rows are below it:

(sums = colSums(paym_area < paym_sh1a))
# [1] 1 3 2

This vector can be used as an index into your results:

values = c(0, 50, 49, 1)
(result = values[sums + 1L])
# [1] 50  1 49