conditionally subset an additional variable and append it to the previous one in R

问题

I'm following up on this excellent answer. I have a function that subsets what (i.e., a variable) user requests out of this dataset.

I was wondering how to add control == TRUE entries IF THEY ARE ABSENT in the output and append those to what the user has requested, otherwise don't do anything.

As an example of control == T absent, suppose user wants to subset entries with type == 4. In this dataset, there are some such entries. As reproducible code and data below show, this is done easily BUT there also are some other entries for which control == TRUE, how can function find and append these control == TRUE entries to its currently-producible output?

As an example of control == T present, suppose user wants to subset entries with prof == 2. In this case control == T entries naturally come with the subset and don't need to be added. So don't do anything.

foo <- function(List, what){       ## The subsetting function

  s <- substitute(what) 

  h <- lapply(List, function(x) do.call("subset", list(x, s)))

  Filter(NROW, h)
}


D <- read.csv("https://raw.githubusercontent.com/rnorouzian/m/master/k.csv", h = T) ## Dataset
L <- split(D, D$study.name) ; L[[1]] <- NULL   ## list by `study.name`

foo(L, type == 4)    ## subsets entries with `type == 4`. BUT how can function `foo` 
                     ## find and append entries with `control == TRUE` to its output?

foo(L, prof == 2)   # entries with `control == TRUE` are already present don't do anything!

回答1:

We can modify the function to

foo <- function(List, what){       ## The subsetting function

  s <- substitute(what) 

  h <- lapply(List, function(x) do.call("subset", list(x, s)))

  h1 <- Filter(NROW, h)
  nm1 <- names(which(!sapply(h1, function(x) any(x$control))))
  if(length(nm1) > 0) {
  h1[nm1]  <- Map(function(x, y) rbind(y, x[x$control, ]), List[nm1], h1[nm1])
  }
  h1

}

foo(L, type == 4) 
foo(L, prof == 2)

来源：https://stackoverflow.com/questions/58739159/conditionally-subset-an-additional-variable-and-append-it-to-the-previous-one-in

标签

list

function

dataframe

subset