symdim: Get symbolic dimension of a statement (as an R code)

In sgsokol/rex2arma: Convert R Code to RcppArmadillo Code

Get symbolic dimension of a statement (as an R code)

Description

Get symbolic dimension of a statement (as an R code)

Usage

symdim(st, env = parent.frame(), dim_tab = NULL)

Arguments

st	A statements, i.e. an item in a list obtained as result of e.g. quote(a+b) or expression(a+b)
env	An environement where a statement can be executed to get its type and structure.
dim_tab	A named list caching symbolic dimensions for R symbols.

Details

If some error occurs, a NA is returned The objects from the statement st are searched for in env if dim_tab is NULL or an object is not there.

Value

a character vector:

1. of legth 2 for a matrix mat, it returns c("nrow(mat)", "ncol(mat)")

2. of length 1 for a vector, e.g. "length(vec)"

3. a string "1" for a scalar

Examples

a=b=c=1:2
lapply(parse(t="x <- a%*%(b+c); y=a+b"), symdim)
# or
symdim(expression(x <- a%*%(b+c))[[1L]])

sgsokol/rex2arma documentation built on May 5, 2023, 12:07 a.m.