Combine formulas

Combining formulas by + or another operator. This is particularly useful for linking tables in the case of table building with formulas.

Usage

combine_formulas(lof, operator = "+", simplify = FALSE, env = parent.frame())

Arguments

lof

list or vector of formulas to be linked

operator

"+" (default), "*", ":" or another operator

simplify

logical value, default FALSE. Determines whether the formula should be expanded and simplified before output or not.

env

the environment for the output formula

Value

model formula

Author

Daniel Lupp and Øyvind Langsrud

Examples

lof1 <- c(~a+b, ~a:c, ~c*d)
combine_formulas(lof1)
#> ~(a + b) + (a:c) + (c * d)
#> <environment: 0x558242bf9cf0>
combine_formulas(lof1, operator = "*")
#> ~(a + b) * (a:c) * (c * d)
#> <environment: 0x558242bf9cf0>
combine_formulas(lof1, simplify = TRUE)
#> ~a + b + c + d + a:c + c:d
#> <environment: 0x558242bf9cf0>

# Intercept is included when needed
lof2 <- c(~a+b -1, ~a:c -1, ~c*d)
combine_formulas(lof2)
#> ~(a + b - 1) + (a:c - 1) + (c * d) + 1
#> <environment: 0x558242bf9cf0>
combine_formulas(lof2, simplify = TRUE)
#> ~a + b + c + d + a:c + c:d
#> <environment: 0x558242bf9cf0>
combine_formulas(lof2[1:2])
#> ~(a + b - 1) + (a:c - 1)
#> <environment: 0x558242bf9cf0>
combine_formulas(lof2[1:2], simplify = TRUE)
#> ~a + b + a:c - 1
#> <environment: 0x558242bf9cf0>