R: Left-hand side checked assignment Provides a way to assign...

%?<-% {dipsaus}

R Documentation

Left-hand side checked assignment Provides a way to assign default values to variables. If the statement '`lhs`' is invalid or `NULL`, this function will try to assign `value`, otherwise nothing happens.

Description

Left-hand side checked assignment Provides a way to assign default values to variables. If the statement 'lhs' is invalid or NULL, this function will try to assign value, otherwise nothing happens.

Usage

lhs %?<-% value

Arguments

`lhs`	an object to check or assign
`value`	value to be assigned if lhs is NULL

Value

Assign value on the right-hand side to the left-hand side if lhs does not exist or is NULL

Examples

# Prepare, remove aaa if exists
if(exists('aaa', envir = globalenv(), inherits = FALSE)){
  rm(aaa, envir = globalenv())
}

# Assign
aaa %?<-% 1; print(aaa)

# However, if assigned, nothing happens
aaa = 1;
aaa %?<-% 2;
print(aaa)

# in a list
a = list()
a$e %?<-% 1; print(a$e)
a$e %?<-% 2; print(a$e)