Function cg = colourgrade_offset(cg) returns the input struct cg after setting cg.offset based on given cg.gradevalues and cg.offsetthreshold. In the process, cg.gradevalues cg.gradeticks cg.gradetexts may be adapted as well; see below. If for an index k cg.gradevalues(k:end) >= cg.offsetthreshold, then cg.offset is set to (k-1). In this case, the values in cg.gradevalues are shifted by (cg.gradevalues(k)-cg.offsetthreshold), an grade interval is appended to it, and cg.gradeticks and cg.gradetexts are set to empty arrays. The latter two arrays can be regenerated by colourgrade_bluered.m (intended) or colourgrade_init.m. If cg.gradevalues(1:end) >= cg.offsetthreshold, then cg.offset is set to 0. If cg.gradevalues(1:end) < cg.offsetthreshold, then cg.offset is set to (length(cg.gradevalues) - 1). At input, the struct cg must have the following fields: cg.gradevalues (column vector of reals) cg.offsetthreshold (scalar) At output, the struc cg contains new or renewed fields: cg.gradevalues (column vector of reals) cg.gradeticks (column vector of booleans) cg.gradetexts (column cell-array of strings) cg.offset (cg.icm_min + cg.offset is the row index to the colourmap where the second part starts) (c) 2026 fabien van mook 2026.08.20 release of this file within package "fvm-colourgrade" under GNU GPLv3+