我正在对我的数据集进行分析，示例数据框 df：
DOY species replicate position SLA PAR temp A1200 susPQ susNPQ FvFm
1: 46 LINGONBERRY 1 LOW 65.75638 19.70906 -2.850833 0.569690 2.147297 0.9321771 0.5263661 562.1016 0.011440 28.02628
2: 46 LINGONBERRY 2 LOW 59.45028 19.78096 -2.850833 0.893840 2.511543 1.0516496 0.5503916 533.6136 0.028930 25.40703
3: 46 LINGONBERRY 3 LOW 59.51058 17.52833 -2.850833 0.731765 2.278927 1.0678274 0.5242824 549.6316 0.020185 46.16188
4: 46 PINE 1 LOW 35.90156 20.85151 -2.850833 1.518910 2.319431 2.2168853 0.4189484 392.6067 0.059280 47.79101
5: 46 PINE 1 TOP 27.29495 90.27197 …