this is amazon dataset for recommendations and when i make pivot using user - item collaborative algorithm the values are NAN, even thogh, there is no nan! in the dataset. and this is a sample [
user_id asin rating
0 AE22BCXGNK7GV24HSZQ2364IRDIQ B087P5DN6R 3.0
1 AE22U642GBGGW7IAZSF26G434GKQ B01F7WA2X0 1.0
2 AE23GZUZ7RSNKV6UCFPFCU2CWYFQ B00R1TAN7I 5.0
3 AE23STWUJTKX4CATKTI3USIZCFHA B00HA72I8S 5.0
4 AE24SIHCAS6X3ZHT7UOM7PJI4ZYA B0BNWXRQ18 4.0], so what is the solution form making pivot matrix?!