as_glycan_structure: Convert to Glycan Structure Vector

In glyrepr: Representation for Glycan Compositions and Structures

Convert to Glycan Structure Vector

Description

Convert an object to a glycan structure vector.

Usage

as_glycan_structure(x, on_failure = c("error", "na"))

Arguments

x	An object to convert to a glycan structure vector. Can be an igraph object, a list of igraph objects, a character vector of IUPAC-condensed strings, or an existing glyrepr_structure object.
on_failure	The failure policy for element-local parsing, validation, and canonicalization errors. "error" preserves the default strict behavior. "na" replaces failed elements with NA and emits one warning that reports their positions and failure reasons. Existing missing elements remain missing without a warning. Vector-level incompatibilities still produce an error.

Details

Character input assumes the natural absolute configuration for unprefixed monosaccharides. Less common configurations use a leading ⁠D-⁠ or ⁠L-⁠, such as D-Fuc, L-Gul, and D-Fucf. Alditols use -ol on the main reducing-end residue, for example ⁠Gal(b1-4)GlcNAc-ol(a1-⁠. The reducing-end anomer annotation remains part of the canonical representation.

Character input supports floating-part blocks before the main IUPAC-condensed structure. ⁠{Neu5Ac(a2-3)}<main>⁠ allows every feasible node outside its own component as a candidate parent, while an explicit ⁠|<parents>⁠ suffix restricts that domain. Parent indices follow residue order in the complete supplied sequence: residues in floating blocks are counted left to right before the main glycan, and substituent blocks add no indices. A floating part may target another floating component or the main tree, but cannot target itself. Indices are remapped to canonical complete sequence order in the result. The suffix is a glyrepr extension to curly-brace IUPAC notation. A singleton candidate set is accepted as input but fully localizes the attachment, so ⁠{Neu5Ac(a2-3)|2}Gal(b1-4)GlcNAc(b1-⁠ canonicalizes to the ordinary structure ⁠Neu5Ac(a2-3)Gal(b1-4)GlcNAc(b1-⁠.

Floating substituents use the same leading-brace and candidate-parent syntax. For example, ⁠{6S}<main>⁠ leaves the sulfated residue unrestricted across all residue nodes, ⁠{6S|1,2}<main>⁠ restricts it to complete-sequence nodes 1 and 2, and ⁠{?S}<main>⁠ also leaves the carbon position unknown. A singleton candidate is normalized into the selected residue's ordinary sub attribute.

Value

A glyrepr_structure object.

Examples

library(igraph)

# Convert a single igraph
graph <- make_graph(~ 1-+2)
V(graph)$mono <- c("GlcNAc", "GlcNAc")
V(graph)$sub <- ""
E(graph)$linkage <- "b1-4"
graph$anomer <- "a1"
as_glycan_structure(graph)

# Convert a list of igraphs
o_glycan_vec <- o_glycan_core_1()
o_glycan_graph <- get_structure_graphs(o_glycan_vec)
as_glycan_structure(list(graph, o_glycan_graph))

# Convert a character vector of IUPAC-condensed strings
as_glycan_structure(c("GlcNAc(b1-4)GlcNAc(b1-", "Man(a1-2)GlcNAc(b1-"))
as_glycan_structure(c("D-Fuc(a1-", "L-Gul(b1-", "D-Fucf(a1-"))
as_glycan_structure("Gal(b1-4)GlcNAc-ol(a1-")

# Parse a floating residue with two candidate parents
floating_iupac <- paste0(
  "{Neu5Ac(a2-3)|2,5}",
  "Gal(b1-4)GlcNAc(b1-2)Man(a1-3)",
  "[Gal(b1-4)GlcNAc(b1-2)Man(a1-6)]",
  "Man(b1-4)GlcNAc(b1-4)GlcNAc(b1-"
)
as_glycan_structure(floating_iupac)

# Preserve valid elements while replacing an invalid element with NA
as_glycan_structure(
  c(valid = "Glc(?1-", invalid = "not-a-structure"),
  on_failure = "na"
)

glyrepr documentation built on Sept. 22, 2026, 5:09 p.m.