lfe (version 2.9-0)

chainsubset: Chain subset conditions

Description

Chain subset conditions

Usage

chainsubset(..., out.vars)

Value

Expression that can be eval'ed to yield a logical subset mask.

Arguments

...

Logical conditions to be chained.

out.vars

character. Variables not in data.frame, only needed if you use variables which are not in the frame. If out.vars is not specified, it is assumed to match all variables starting with a dot ('.').

Details

A set of logical conditions are chained, not and'ed. That is, each argument to chainsubset is used as a filter to create a smaller dataset. Each subsequent argument filters further. For independent conditions this will be the same as and'ing them. I.e. chainsubset(x < 0 , y < 0) will yield the same subset as (x < 0) & (y < 0). However, for aggregate filters like chainsubset(x < mean(y), x > mean(y)) we first find all the observations with x < mean(y), then among these we find the ones with x > mean(y). The last mean(y) is now conditional on x < mean(y).

Examples

set.seed(48)
N <- 10000
dat <- data.frame(y = rnorm(N), x = rnorm(N))
# It's not the same as and'ing the conditions:
felm(y ~ x, data = dat, subset = chainsubset(x < mean(y), y < 2 * mean(x)))
felm(y ~ x, data = dat, subset = chainsubset(y < 2 * mean(x), x < mean(y)))
felm(y ~ x, data = dat, subset = (x < mean(y)) & (y < 2 * mean(x)))
lm(y ~ x, data = dat, subset = chainsubset(x < mean(y), x > mean(y)))