Filament line mass function (FLMF, ΔN/ΔlogM_line), derived from the sample of filament chunks in the California GMC. The error bars represent statistical uncertainties ($\sqrt{\text{Δ}N}$) in the numbers of filament chunks in each bin. The FLMF based on filament chunks with length L ~ 0.1 pc and contrasts C > 0.2 are shown by the blue histogram; the FLMF of chunks with L ~ 0.1 pc and C > 0.4 by the green histogram. These two FLMFs coincide for M_line > 8 M_⊙ pc⁻¹. Above an estimated completeness limit of M_line ≈ 10 M_⊙ pc⁻¹ (gray filled area), the filament chunk sample is considered 80% complete (see Appendix B). The FLMF can be fitted by a power law above 10 M_⊙ pc⁻¹ with an index of −1.4 ± 0.1 (red solid line). For comparison, the FLMF of filament chunks with L ~ 0.2 pc and C > 0.2 is shown as a purple dashed histogram; the FLMF of chunks with L ~ 0.2 pc and C > 0.4 as an orange dashed histogram.