Nickel Price Forecast Based on the LSTM Neural Network Optimized by the Improved PSO Algorithm

Table 2

The Ljung–Box test results of first-order difference sequences.

Lag	AC	Q	-value
1.0	0.335056	13.137734	0.000289
2.0	0.137655	15.375058	0.000459
3.0	−0.047252	15.641057	0.001343
4.0	0.094434	16.713127	0.002197
5.0	0.134068	18.893789	0.002012
6.0	0.033009	19.027203	0.004118
7.0	−0.080867	19.835415	0.005936
8.0	−0.115688	21.505096	0.005920
9.0	−0.074676	22.207423	0.008244
10.0	−0.000595	22.207468	0.014082