我试图在r中将表联接到主表，但是联接到主表的表中的观察值均为NA。
例如，这是两个表（main_c）数据帧
species3Alpha month year landing_sites fishingunits.canoetype sum_C_jsmycv sum_f_jmycv
ALA 1 2019 BIG FANTE TOWN BEACH Fante 225 12
ALA 1 2019 BIG FANTE TOWN BEACH Kru 21 2
ALA 1 2019 Cestos Kru Beach Kru 43 8
ALA 1 2019 FANTI BEACH Fante 1350 2
ALA 1 2019 GARRAWAY FANTI BEACH Fante 1104 2
ALA 1 2019 Old kru town Fante 150 6
ALA 1 2019 Popo Beach Kru 1 2
ALA 2 2019 Banjor Beach Kru 275 2
ALA 2 2019 BIG FANTE TOWN BEACH Fante 84 8
ALA 2 2019 Cestos Kru Beach Kru 35.625 8
ALA 2 2019 Old kru town Kru 10 2
ALA 3 2019 Garraway fante beach Fante 682 1
ANE 1 2019 Popo Beach Kru 15 2
ANE 2 2019 Ceastos City Fanti Beach Fante 3588 2
ANE 2 2019 Garraway fanti beach Fante 165 2
AUR 1 2019 Cestos Kru Beach Kru 35 2
这是（F_mycv）数据框
canoe_type landing_sites B_ycv F_mycv
1 102 KRU BEACH (ROBERTSPORT) 102 1219.92
1 103 BOMOJA/KENEMA BEACH 1 11.96
1 104 SOWEE BEACH 29 346.84
1 105 TAILOR (FANTI BEACH) 53 633.88
1 106 TAILOR (KRU BEACH) 48 574.08
1 107 FUMBAH TOWN BEACH 18 215.28
1 201 TUMA TOWN BEACH 29 346.84
1 202 ROYCEVILLE BEACH 35 418.6
1 301 BANJOR BEACH 40 478.4
1 302 POINT FOUR BEACH 184 2200.64
1 303 WEST POINT BEACH 257 3073.72
1 304 BERNARD BEACH 47 562.12
1 305 KING GRAY BEACH 103 1231.88
1 306 ELWA BEACH 101 1207.96
1 307 KPEKOR BEACH 48 574.08
1 401 BEN'S TOWN 3 35.88
1 402 FLOKO TOWN BEACH 4 47.84
main_c <- main_c %>% left_join(F_mycv)
这是我得到的结果。
species3Alpha month year landing_sites fishingunits.canoetype sum_C_jsmycv sum_f_jmycv canoe_type B_ycv F_mycv
ALA 1 2019 BIG FANTE TOWN BEACH Fante 225 12 NA NA NA
ALA 1 2019 BIG FANTE TOWN BEACH Kru 21 2 NA NA NA
ALA 1 2019 Cestos Kru Beach Kru 43 8 NA NA NA
ALA 1 2019 FANTI BEACH Fante 1350 2 NA NA NA
ALA 1 2019 GARRAWAY FANTI BEACH Fante 1104 2 NA NA NA
ALA 1 2019 Old kru town Fante 150 6 NA NA NA