How to take monthly of time series using loop

The time series is given:

2004  1  1  0.00183  0.000244  -0.004387
2004   1  1  0.000605  -0.00152  0.004283
2004  1   1  0.000961  0.000507  0.000924
2004  1       1  0.000386  0.001633  0.003944
2004  1   1  0.000972  -0.00047  -5.50000000000000e-05
2004  1  1  0.002107  -0.000794  0.005815
2004  1  1  0.000743  1.20000000000000e-05  0.005226
2004  1  1  0.002128  0.000259  0.010336
2004  1  1  0.002494  0.000205  0.003747
2004   1  1  0.001899  0.001012  0.003698
2004  1  1  0.001504  0.000238  0.005318
2004  1  1  0.00105  0.000474  0.007499
2004  1  1  0.002845  0.003381  0.009119
2004  1  1  0.002611  -7.30000000000000e-05  0.0069
2004  1  1  0.001306  0.001613  0.00447
2004  1  1  -8.00000000000000e-06  0.00123  -0.000189
2004  1  1  0.002357  -0.000544  0.009731
2004  1  1  0.002023  0.000703  0.004792
2004  1   1  0.001828  -0.000241  0.007092
2004  1  1  0.003543  5.00000000000000e-06  0.008983
2004  1  1  0.001939  0.001422  0.006204
2004   1  1  0.003294  0.001388  0.006574
2004  1  1  0.00144  0.000995  0.010025
2004  1  1  0.003095  0.000321  0.005125
2004  1  1  0.002601  1.70000000000000e-05  -0.001874
2004  1  1  0.001696  -0.000246  0.006686
2004  1  1  0.002782  0.00022  0.002957
2004   1  1  0.004027  -0.001583  0.004167
2004  1  1  0.002812  0.001203  0.011278
2004  1  1  0.003018  -0.000721  0.003528
2004  1  1  0.003213  -0.000944  0.004279
2004  2  2  0.002339  0.000602  0.00506
2004  2  2  0.001814  0.002648  0.01039
2004  2  2  0.00417  0.000725  0.010261
2004  2  2  0.002505  -0.000149  0.008721
2004  2  2  0.004151  0.001368  0.007122
2004   2  2  0.003226  0.000314  0.008232
2004  2  2  0.004381  -0.00074  0.013943
2004  2  2  0.004677  0.001997  0.008733
2004  2  2  0.004932  0.002123  0.010404
2004  2  2  0.003488  0.00152  0.010224
2004  2  2  0.003683  -0.000554  0.009835
2004  2  2  0.002489  -5.70000000000000e-05  0.015106
2004  2  2  0.003204  -0.001761  0.014296
2004  2  2  0.00304  6.50000000000000e-05  0.019437
2004  2   2  0.001525  -2.80000000000000e-05  0.012417
2004  2  2  0.00253  0.000538  0.014618
2004  2  2  0.003516  0.000415  0.017568
2004  2  2  0.004281  -0.001479  0.016839
2004  2  2  0.004647  0.000368  0.010799
2004  2  2  0.004262  0.001064  0.01321
2004  2  2  0.004718  -0.00058  0.01774
2004  2  2  0.006033  7.00000000000000e-06  0.009581
2004  2  2  0.004009  -0.000177  0.015122
2004  2  2  0.004144  0.000299  0.020492
2004  2  2  0.003719  -0.001204  0.019063
2004  2  2  0.002645  9.20000000000000e-05  0.019793
2004  2  2  0.00234  -0.001831  0.009724
2004  2  2  0.003636  -0.000215  0.014094
2004  2  2  0.000941  -0.000359  0.012545
2004  3  3  0.002557  -0.000512  0.010485
2004  3  3  0.003202  -0.000436  0.012646
2004  3  3  0.003748  0.000671  0.010406
2004  3  3  0.003263  -0.001303  0.015117
2004  3  3  0.001548  0.000903  0.018938
2004  3  3  0.003624  -8.00000000000000e-05  0.016948
2004  3  3  0.003689  -0.000364  0.015519
2004  3  3  0.003415  0.000153  0.015609
2004  3  3  0.00243  0.000139  0.01701
2004  3  3  0.002996  3.50000000000000e-05  0.01741
2004  3  3  0.003031  0.001682  0.014371
2004  3  3  0.003277  -0.001282  0.015711
2004  3  3  0.002772  8.40000000000000e-05  0.015662
2004  3  3  0.001867  0.000131  0.016902
2004  3  3  0.004283  0.000737  0.017173
2004  3  3  0.002558  0.001174  0.016494
2004  3  3  0.004644  0.00127  0.021894
2004  3  3  0.005249  -0.000424  0.020605
2004  3  3  0.002935  0.000423  0.020905
2004  3  3  0.00485  0.001899  0.015756
2004  3  3  0.006046  -0.001534  0.016056
2004  3  3  0.004311  0.000652  0.020097
2004  3  3  0.005686  0.002018  0.014757
2004  3  3  0.003502  -0.001645  0.032318
2004  3  3  0.006277  -0.001669  0.015378
2004  3  3  0.006343  -0.001122  0.014229
2004  3  3  0.003288  -0.000606  0.00465
2004  3  3  0.004704  0.00311  0.01063
2004  3  3  0.005849  1.70000000000000e-05  0.010701
2004  3  3  0.005095  -7.00000000000000e-06  0.006811
2004  3  3  0.00316  0.000949  0.013402
2004  4  4  0.004155  0.001486  0.011922
2004  4  4  0.005581  -0.001488  0.010273
2004  4  4  0.005557  0.001409  0.013983
2004  4  4  0.007092  0.001845  0.016064
2004  4  4  0.005157  0.002332  0.007935
2004  4  4  0.004543  -0.000132  0.005265
2004  4  4  0.002788  0.001724  0.008736
2004  4  4  0.002604  0.000911  0.006886
2004  4  4  0.003029  -0.000243  0.009897
2004  4  4  0.003455  0.000744  0.005637
2004  4  4  0.008596  0.000637  0.011538
2004  4  4  0.001261  0.000163  0.008399
2004  4  4  0.001062  -0.000634  -0.00099
2004  4  4  0.003097  -0.000688  0.000921
2004  4  4  0.003803  -0.000311  0.001831
2004  4  4  0.000818  -3.50000000000000e-05  0.004402
2004  4  4  0.003234  -0.000109  0.001352
2004  4  4  0.002669  -0.000382  0.002883
2004  4  4  0.003215  -0.000556  0.004213
2004  4  4  0.00063  0.00118  0.004834
2004  4  4  0.004965  0.000977  0.003644
2004  4  4  0.003581  0.001913  0.010575
2004  4  4  0.003722  0.000946  0.012386
2004  4  4  0.004437  -0.000668  0.018867
2004  4  4  0.003683  -0.000981  0.001497
2004  4  4  0.003168  -0.001065  0.001888
2004   5  5  0.002751  0.000404  0.006631
2004  5  5  0.003306  0.0016  0.012171
2004  5  5  0.003432  0.000586  0.009522
2004  5  5  0.001857  0.002933  0.011873
2004  5  5  0.003433  -0.001171  0.008803
2004  5  5  0.003318  0.000205  0.029124
2004  5  5  0.002263  0.000842  0.012004
2004  5  5  0.003029  -0.000322  0.010115
2004  5  5  0.003964  0.003325  0.004145
2004   5  5  0.002005  -0.001043  0.007216
2004  5  5  0.002971  0.001314  0.006207
2004  5  5  0.000116  0.00334  0.004497
2004  5  5  0.003182  0.000587  0.009018
2004  5  5  0.002917  0.003083  0.010509
2004  5  5  0.001092  -0.001721  0.003519
2004  5  5  0.002258  0.000606  0.00415
2004  5  5  0.000733  0.002502  0.00736
2004  5  5  0.001949  -0.002001  0.003021
2004   5  5  0.002004  -0.002035  -0.011269
2004  5  5  6.00000000000000e-05  -0.001369  0.002682
2004  5  5  0.003965  -0.000392  -0.000108
2004  5  5  0.003551  0.000284  0.003833
2004  5  5  0.002466  -0.003109  -0.017827
2004  5  5  0.003661  -0.000963  -0.022946
2004  5  5  0.001777  -0.001847  0.000935
2004  5  5  0.002442  0.00037  -0.002825
2004  6  6  0.003568  -0.003454  -0.005284
2004   6  6  0.001843  -0.001907  0.008646
2004  6  6  0.001349  -0.000581  -0.003793
2004  6  6  0.000744  -0.003284  -0.000113
2004  6  6  -0.00072  0.000192  0.008248
2004  6  6  0.001075  -0.000552  -0.001472
2004  6  6  0.00064  -0.000685  0.006949
2004  6  6  0.002616  2.10000000000000e-05  -0.001371
2004  6  6  0.004251  -0.000732  -0.0005
2004  6  6  0.004082  0.00094  0.004061
2004   6  6  0.001968  0.001007  0.003962
2004  6  6  0.003323  -0.000737  0.003312
2004  6  6  0.003829  0.00056  0.006183
2004  6  6  0.002104  -0.000914  -0.006847
2004  6  6  0.002569  -0.001118  0.015024
2004  6  6  0.000495  -2.10000000000000e-05  0.002014
2004  6  6  0.001436  -9.00000000000000e-06  0.009595
2004  6  6  0.003131  -0.000702  -0.001494
2004  6  6  0.001037  -0.001356  -0.004243
2004   6  6  0.004102  -0.000729  -0.010233
2004  6  6  0.002758  0.000347  0.001078
2004  6  6  0.003643  0.000263  -0.001482
2004  6  6  0.002348  -0.00195  -0.007361
2004  6  6  0.001044  -0.001524  -0.006211
2004  6  6  0.001169  -0.001727  -0.00835
2004  6  6  0.001465  -0.000901  -0.00956
2004  6  6  0.00114  -0.001715  -0.007659
2004  6  6  0.000556  -0.001818  -0.008579
2004   6  6  0.000991  -0.002292  -0.001538
2004  7  7  0.001167  -0.003755  -0.001987
2004  7  7  0.002792  -0.004139  -0.000157
2004  7  7  0.001077  -0.000143  -0.009116
2004  7  7  0.004223  -0.002426  -0.004396
2004  7  7  0.001298  -1.00000000000000e-05  -0.003905
2004  7  7  0.000624  -0.000674  -0.002025
2004  7  7  0.002539  -0.003287  -0.013444
2004  7  7  0.003065  -0.001691  -0.014394
2004   7  7  0.00123  -0.001674  -0.013243
2004  7  7  0.000566  -0.002768  -0.015433
2004  7  7  0.000371  -0.003362  -0.015882
2004  7  7  -0.000104  -0.004375  -0.018991
2004  7  7  -0.000118  -0.000899  -0.022281
2004  7  7  -0.000323  -0.001302  -0.01879
2004  7  7  0.001113  -0.001416  -0.01626
2004   7  7  -0.001202  -0.00019  -0.019839
2004  7  7  0.001334  -0.002793  -0.020419
2004   7  7  0.000849  -0.002157  -0.022448
2004   7  7  0.000265  -0.0008  -0.020368
2004  7  7  0.0005  -0.001934  -0.019977
2004  7  7  9.50000000000000e-05  -0.001157  -0.019857
2004  7  7  -0.000589  -0.002701  -0.020766
2004  7  7  -0.001614  0.000185  -0.018755
2004  7  7  -0.000128  -0.000788  -0.022645
2004  7  7  -0.002263  -0.001522  -0.029264
2004  7  7  0.000273  -0.003865  -0.019934
2004  7  7  -0.002882  -0.001149  -0.019163
2004  7  7  -0.000256  -0.001162  -0.012633
2004  7  7  0.000999  -0.003026  -0.006102
2004   7  7  0.001314  -0.00211  -0.015532
2004   7  7  -0.00138  -0.002083  -0.014451
2004  8  8  0.000565  -0.000877  -0.013701
2004  8  8  0.003241  7.90000000000000e-05  -0.02182
2004  8  8  0.000696  -0.001324  -0.014209
2004  8  8  0.001472  -0.003098  -0.019979
2004  8  8  -0.001063  -0.002391  -0.015568
2004  8  8  0.001213  -0.001955  -0.013238
2004  8  8  -0.000632  -0.001869  -0.010377
2004  8  8  0.001083  -7.20000000000000e-05  -0.016617
2004  8  8  0.002139  -0.002196  -0.006196
2004  8  8  0.000914  -0.001599  -0.012146
2004  8  8  -6.00000000000000e-05  -0.002163  -0.007565
2004  8  8  0.003715  0.000323  0.003045
2004  8  8  0.000261  -0.00141  -0.004234
2004  8  8  0.000476  -0.001404  -0.006863
2004  8  8  0.002331  -0.003648  -0.008833
2004  8  8  -0.002513  -0.001661  -0.006922
2004  8  8  0.000842  -0.001605  -0.007702
2004  8  8  0.002538  -0.000128  -0.009941
2004  8  8  -0.000727  -0.001142  -0.012061
2004  8  8  0.001159  -0.003026  -0.01303
2004  8  8  0.000494  -0.004509  -0.00336
2004  8  8  -0.00029  -0.000383  -0.013859
2004  8  8  -0.001295  -0.000506  -0.005379
2004  8  8  0.00117  0.00013  0.001552
2004  8  8  0.001666  0.000776  0.006383
2004  8  8  0.000211  -0.001337  -0.019627
2004  8  8  -0.001423  -0.000691  -0.008536
2004  8  8  0.001072  -0.002854  -0.011546
2004  8  8  0.002478  -0.000398  -0.004815
2004  8  8  -0.000877  0.000508  -0.002615
2004  8  8  -0.000871  -0.000195  -0.012214
2004  9  9  0.001544  -0.002509  -0.010724
2004  9  9  0.000459  -0.001663  -0.018523
2004  9  9  0.001865  -0.002596  -0.009093
2004  9  9  0.00013  -0.00031  -0.010622
2004  9  9  -0.000544  -0.000873  -0.014591
2004  9  9  -0.000879  -0.000757  -0.009091
2004  9  9  -0.001973  -0.000141  -0.00565
2004  9  9  0.000532  -0.001014  -0.00662
2004  9  9  0.001148  -0.002368  -0.013169
2004  9  9  0.000673  -5.10000000000000e-05  -0.007929
2004  9  9  0.000168  -4.50000000000000e-05  -0.008138
2004  9  9  -0.001436  -0.000768  -0.013418
2004  9  9  -0.000281  -0.000102  -0.006277
2004  9  9  0.001635  -0.001416  -0.004917
2004  9  9  -0.00105  -0.002349  -0.009566
2004  9  9  -0.001584  0.000427  -0.004395
2004  9  9  -0.001169  -0.001766  -0.001315
2004  9  9  -0.000743  -0.00034  -0.007784
2004  9  9  -0.001378  0.000407  -0.003584
2004  9  9  -0.001273  -0.000157  -0.004793
2004  9  9  -0.000307  -0.000961  -0.004793
2004  9  9  -0.000252  0.001406  -0.016082
2004  9  9  -0.000946  0.000882  -0.009102
2004  9  9  -0.001361  0.000309  -0.009431
2004  9  9  0.000955  -0.000165  0.003879
2004  9  9  0.00268  -0.000339  -0.00921
2004  9  9  -0.000864  -0.000722  -0.003929
2004  9  9  0.001771  0.003064  -0.002839
2004  9  9  6.60000000000000e-05  -0.00041  -0.020198
2004  9  9  -0.000568  0.000497  -0.005868
2004  10  10  0.004807  -0.001387  -0.008017
2004  10  10  -0.000597  0.00187  -0.004757
2004  10  10  -0.001312  0.000666  0.004114
2004  10  10  0.001314  0.000882  -0.003646
2004  10  10  -0.000921  0.000379  -0.009755
2004  10  10  -0.0025  0.001772  -0.019094
2004  10  10  -0.000865  0.000928  -0.010953
2004  10  10  -0.001749  -0.000836  -0.012613
2004  10  10  -0.001684  0.000431  -0.014142
2004  10  10  -0.002298  0.000537  -0.011782
2004  10  10  0.000227  -0.000186  -0.009461
2004  10  10  0.000893  -2.00000000000000e-05  -0.005481
2004  10  10  -0.002872  -0.000714  -0.01015
2004  10  10  -0.002476  0.000843  -0.00906
2004  10  10  0.000489  0.001229  -0.008129
2004  10  10  -0.003406  0.002655  -0.002439
2004  10  10  -0.00063  0.000942  -0.002718
2004  10  10  -0.002235  0.001058  -0.013407
2004  10  10  -0.002889  0.001075  0.001813
2004  10  10  0.001596  0.004231  0.007934
2004  10  10  -0.003538  0.002487  0.016034
2004  11  11  -0.000885  -0.000701  -0.002985
2004  11  11  -0.000629  0.000776  0.002805
2004  11  11  -0.000654  0.001302  0.004246
2004  11  11  -0.000929  0.002958  0.009406
2004  11  11  -0.000903  0.002595  0.005497
2004  11  11  -0.000307  0.000751    -9.30000000000000e-05
2004  11  11  -0.000632  4.80000000000000e-05  0.001908
2004  11  11  0.000933  -0.000666  0.003558
2004  11  11  -0.001221  0.00031         0.002209
2004  11  11  0.000774  0.001037  0.005659
2004  11  11  0.00039  0.000323  0.00316
2004  11  11  0.000555  0.00343  0.005361
2004  11  11  0.002111  0.000506  0.007781