Hi everyone,

I am not sure if this is a coding question or not, but maybe I do something wrong when I try to hold for time (monthly)

When I run my regression without holding time fixed I get very normal results but when i try to hold company and time fix my number goes up to -30 ("zfund") All other variables also increase dramatically when compared to the other regressions without time fix.
My results slightly change when I use the xtreg command.

HTML Code:
. reg rirf mktrf smb hml cma rmw zfund i.company i.modate if bank==1, vce(robust)
note: 714.modate omitted because of collinearity
note: 715.modate omitted because of collinearity
note: 716.modate omitted because of collinearity
note: 717.modate omitted because of collinearity
note: 718.modate omitted because of collinearity
note: 719.modate omitted because of collinearity

Linear regression                               Number of obs     =      1,425
F(108, 1316)      =      11.50
Prob > F          =     0.0000
R-squared         =     0.4454
Root MSE          =     6.2579


Robust
rirf       Coef.   Std. Err.      t    P>t     [95% Conf. Interval]

mktrf   -7.741088   2.891952    -2.68   0.008    -13.41443   -2.067747
smb    83.13031   26.54097     3.13   0.002     31.06308    135.1975
hml    29.64834   9.107067     3.26   0.001     11.78239     47.5143
cma   -91.93764   29.74267    -3.09   0.002    -150.2859    -33.5894
rmw    16.34663   5.399005     3.03   0.003     5.755035    26.93823
zfund   -30.49034   9.830907    -3.10   0.002     -49.7763   -11.20438

company
2    -.2254826   .7400578    -0.30   0.761    -1.677305    1.226339
3     .6018272    .701427     0.86   0.391    -.7742101    1.977864
4    -.2621059   .7682079    -0.34   0.733    -1.769152     1.24494
5    -.8889629     .83551    -1.06   0.288     -2.52804    .7501141
6     .6871316   .6355133     1.08   0.280    -.5595982    1.933861
8     .7561471   .6202832     1.22   0.223    -.4607047    1.972999
9     .2336869   1.169095     0.20   0.842    -2.059806     2.52718
10     .0937355   .7444822     0.13   0.900    -1.366766    1.554237
12     .8158824   .6943988     1.17   0.240    -.5463672    2.178132
13     1.019205   .6837043     1.49   0.136    -.3220642    2.360475
16     .4957002    .819849     0.60   0.546    -1.112653    2.104054
18     1.346019   .8399703     1.60   0.109    -.3018083    2.993846
22    -.4672312   .8978365    -0.52   0.603    -2.228578    1.294116
23     .1977232    .732314     0.27   0.787    -1.238907    1.634354

modate
626     222.2949   71.74912     3.10   0.002     81.53979    363.0501
627     134.6272   45.69678     2.95   0.003     44.98072    224.2737
628     652.8424   211.0267     3.09   0.002      238.857    1066.828
629     144.3677   46.00811     3.14   0.002     54.11043    234.6249
630     73.92128   25.33666     2.92   0.004     24.21662    123.6259
631    -405.2951   128.9413    -3.14   0.002    -658.2481   -152.3421
632    -146.7154   48.25323    -3.04   0.002    -241.3771   -52.05379
633      290.815   92.56789     3.14   0.002     109.2183    472.4118
634     372.3913   117.8889     3.16   0.002     141.1205    603.6621
635    -143.4482   45.42443    -3.16   0.002    -232.5604   -54.33598
636     222.1932   72.27017     3.07   0.002     80.41582    363.9705
637     141.2558   43.50198     3.25   0.001     55.91501    226.5966
638       963.34   310.3925     3.10   0.002     354.4218    1572.258
639      755.214   243.6914     3.10   0.002      277.148     1233.28
640    -69.44905   23.59605    -2.94   0.003     -115.739   -23.15907
641     383.8979    123.281     3.11   0.002     142.0491    625.7467
642     -31.5048   9.671183    -3.26   0.001    -50.47742   -12.53218
643    -1475.425   470.4333    -3.14   0.002    -2398.306   -552.5436
644      168.261    55.6351     3.02   0.003     59.11779    277.4041
645     313.8667   103.9872     3.02   0.003     109.8678    517.8655
646    -31.43098   9.650449    -3.26   0.001    -50.36292   -12.49903
647     28.61077   13.01828     2.20   0.028     3.071926    54.14962
648    -21.92804   10.66222    -2.06   0.040    -42.84486   -1.011229
649     480.9861    156.142     3.08   0.002     174.6716    787.3005
650    -422.4824   136.6897    -3.09   0.002    -690.6358    -154.329
651      134.122   44.75692     3.00   0.003     46.31926    221.9247
652    -276.7555   91.15423    -3.04   0.002     -455.579   -97.93206
653     165.3584   55.49897     2.98   0.003     56.48223    274.2345
654    -133.5545   42.40651    -3.15   0.002    -216.7463   -50.36277
655     407.6095   131.6857     3.10   0.002     149.2726    665.9464
656     96.83652   30.80273     3.14   0.002     36.40869    157.2643
657     576.5107   182.4324     3.16   0.002     218.6206    934.4008
658     551.4193   176.8529     3.12   0.002     204.4749    898.3638
659     8.824968   3.843126     2.30   0.022     1.285646    16.36429
660     614.1406   195.4389     3.14   0.002     230.7348    997.5465
661    -628.8514   199.1306    -3.16   0.002    -1019.499   -238.2033
662    -497.7888    160.854    -3.09   0.002     -813.347   -182.2306
663     123.5451   43.50337     2.84   0.005     38.20159    208.8887
664     470.0544   151.0653     3.11   0.002     173.6992    766.4095
665    -493.9739   159.4835    -3.10   0.002    -806.8435   -181.1042
666     381.0563   119.1389     3.20   0.001     147.3333    614.7793
667     526.7112   170.5474     3.09   0.002     192.1367    861.2858
668     195.4699   59.98222     3.26   0.001     77.79863    313.1411
669     340.2443   111.3667     3.06   0.002     121.7686      558.72
670     -129.214   43.35516    -2.98   0.003    -214.2668   -44.16123
671    -306.4041   100.7365    -3.04   0.002    -504.0258   -108.7824
672     679.6763   221.8322     3.06   0.002      244.493     1114.86
673    -39.66966    11.1847    -3.55   0.000    -61.61144   -17.72787
674     106.6453    38.0042     2.81   0.005     32.08988    181.2007
675    -189.4463   58.17123    -3.26   0.001    -303.5648   -75.32784
676    -25.63161   11.04307    -2.32   0.020    -47.29556   -3.967657
677     1098.561   358.0568     3.07   0.002     396.1364    1800.985
678    -308.2393   100.4527    -3.07   0.002    -505.3042   -111.1745
679     -629.049   201.2644    -3.13   0.002    -1023.883   -234.2148
680      79.9836   28.74794     2.78   0.005     23.58681    136.3804
681     653.5069   213.4947     3.06   0.002     234.6797    1072.334
682      324.441   106.5399     3.05   0.002     115.4345    533.4476
683    -457.9802    145.974    -3.14   0.002    -744.3473   -171.6131
684    -8.343466   4.889446    -1.71   0.088    -17.93543    1.248493
685    -288.4626   92.77054    -3.11   0.002    -470.4569   -106.4683
686    -297.2549   95.05027    -3.13   0.002    -483.7215   -110.7883
687    -488.4962    158.951    -3.07   0.002    -800.3211   -176.6712
688    -194.6549   63.59026    -3.06   0.002    -319.4042   -69.90552
689    -59.08523   18.86541    -3.13   0.002    -96.09479   -22.07567
690     543.3927   175.4882     3.10   0.002     199.1255      887.66
691     375.2523   122.2663     3.07   0.002     135.3941    615.1105
692    -320.1725   101.9362    -3.14   0.002    -520.1478   -120.1972
693    -276.3201   88.92715    -3.11   0.002    -450.7745   -101.8656
694    -159.5069   50.74582    -3.14   0.002    -259.0585   -59.95541
695     59.01116   20.78509     2.84   0.005     18.23562    99.78669
696      215.481   69.60309     3.10   0.002     78.93589    352.0262
697     111.0419   36.12761     3.07   0.002     40.16791    181.9159
698     40.92566   14.12682     2.90   0.004      13.2121    68.63921
699     549.7019   180.8562     3.04   0.002     194.9039    904.4998
700     334.5527   110.4683     3.03   0.003     117.8395    551.2658
701     81.90609   25.88978     3.16   0.002     31.11634    132.6958
702    -248.5268   81.43264    -3.05   0.002    -408.2787    -88.7748
703     23.31244   11.11368     2.10   0.036      1.50998     45.1149
704      36.1108   15.41594     2.34   0.019     5.868287    66.35331
705     359.4327    117.863     3.05   0.002     128.2129    590.6525
706     183.2765    56.3681     3.25   0.001     72.69539    293.8577
707       246.19   81.30779     3.03   0.003     86.68296    405.6971
708     100.9648   34.43503     2.93   0.003     33.41125    168.5184
709     698.7783   225.6664     3.10   0.002     256.0732    1141.483
710     209.0761   69.03158     3.03   0.003     73.65212       344.5
711     -359.826   116.8699    -3.08   0.002    -589.0977   -130.5543
712    -171.9024   55.14543    -3.12   0.002    -280.0849   -63.71984
713     954.6183   308.8173     3.09   0.002     348.7903    1560.446
714            0  (omitted)
715            0  (omitted)
716            0  (omitted)
717            0  (omitted)
718            0  (omitted)
719            0  (omitted)

_cons    75.27633   23.56857     3.19   0.001     29.04025    121.5124
Could this be because of my sample size of only 14 companies? But if so, I also tried it on a sample size of about 100 and I get similar results (odd numbers)

Thanks everyone.