Environmental Systems Research

Table 1 Results summary—NO₂ data missing at random

From: Spectral methods for imputation of missing air quality data

	KSVD	DCT	EM	MN	Sp	Lin	NN
MSE (ppb)
Low	4.54	5.77	4.60	5.79	1.68	1.51	2.04
Mid	5.64	7.47	5.69	5.79	2.24	1.88	2.31
High	9.80	12.48	9.89	5.79	4.9	3.29	3.69
Diff (ppb)
Low	40.12	51.81	44.06	113.6	54.23	40.5	109.3
Mid	58.26	73.40	62.05	136.9	153.5	58.97	71.77
High	96.83	128.4	95.47	143.9	622.6	95.39	51.84
STD (ppb)
Low	−0.17	−0.11	−0.18	−15.56	−14.89	−14.97	−14.91
Mid	−0.72	−0.55	−0.75	−17.09	−14.52	−15.16	−14.91
High	−2.28	−2.71	−2.23	−19.40	−8.59	−15.66	−14.92
Time (sec)
Low	303	0.23	26.22	1.78 × 10 ⁻⁵	3 × 10⁻³	2 × 10⁻⁴	7.89 × 10⁻⁵
Mid	272	0.96	17.07	1.01 × 10 ⁻⁵	2.5 × 10⁻³	2 × 10⁻⁴	1.4 × 10⁻⁴
High	164	6.6	6.59	2.03 × 10 ⁻⁵	1.5 × 10⁻³	2.7 × 10⁻⁴	4.1 × 10⁻⁴

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