[R] aggregate

[Sherri Heck]

Dear All-

I have a dataset that is comprised of the following:


doy yr mon day hr hgt1 hgt2 hgt3 co21 co22 co23 sig1 sig2 sig3 dif flag

244.02083 2005 09 01 00 2.6 9.5 17.8 375.665 373.737 373.227 3.698 1.107 
0.963 -0.509 PRE
244.0625 2005 09 01 01 2.6 9.5 17.8 393.66 384.773 379.466 15.336 11.033 
5.76 -5.307 PRE
244.10417 2005 09 01 02 2.6 9.5 17.8 411.162 397.866 387.755 6.835 5.61 
6.728 -10.112 PRE
244.14583 2005 09 01 03 2.6 9.5 17.8 417.78 395.579 392.838 13.897 4.631 
4.998 -2.741 PRE
244.1875 2005 09 01 04 2.6 9.5 17.8 420.844 408.747 401.923 5.673 7.154 
4.312 -6.823 PRE
244.22917 2005 09 01 05 2.6 9.5 17.8 414.714 404.652 401.141 3.72 3.296 
4.028 -3.511 PRE
244.27083 2005 09 01 06 2.6 9.5 17.8 423.77 405.623 401.815 5.23 2.808 
2.653 -3.808 PRE
244.3125 2005 09 01 07 2.6 9.5 17.8 415.703 406.324 399.115 4.189 3.441 
3.648 -7.209 PRE
244.35417 2005 09 01 08 2.6 9.5 17.8 416.343 403.47 398.71 4.344 2.145 
1.482 -4.76 PRE
244.39583 2005 09 01 09 2.6 9.5 17.8 413.512 401.195 398.106 3.941 2.663 
1.905 -3.089 PRE
244.4375 2005 09 01 10 2.6 9.5 17.8 419.308 406.377 401.889 3.443 2.888 
1.471 -4.488 PRE
244.47917 2005 09 01 11 2.6 9.5 17.8 415.864 406.004 400.702 2.082 1.858 
2.507 -5.302 PRE
244.52083 2005 09 01 12 2.6 9.5 17.8 413.062 405.385 400.509 4.142 2.041 
2.52 -4.877 PRE
244.5625 2005 09 01 13 2.6 9.5 17.8 407.566 396.001 392.831 7.445 5.028 
3.691 -3.17 PRE
244.60417 2005 09 01 14 2.6 9.5 17.8 395.374 385.151 384.275 8.889 2.422 
2.115 -0.876 PRE
244.64583 2005 09 01 15 2.6 9.5 17.8 383.308 382.984 383.43 1.546 1.168 
1.529 0.446 PRE
244.6875 2005 09 01 16 2.6 9.5 17.8 379.112 379.168 379.209 1.475 1.478 
1.365 0.041 PRE
244.72917 2005 09 01 17 2.6 9.5 17.8 372.948 373.424 373.737 1.52 1.721 
1.827 0.313 PRE
244.77083 2005 09 01 18 2.6 9.5 17.8 373.435 373.479 373.498 0.431 0.29 
0.187 0.019 PRE
244.8125 2005 09 01 19 2.6 9.5 17.8 374.082 374.11 374.104 0.264 0.227 
0.242 -0.006 PRE
244.85417 2005 09 01 20 2.6 9.5 17.8 373.619 373.592 373.528 0.221 0.253 
0.225 -0.064 PRE
244.89583 2005 09 01 21 2.6 9.5 17.8 373.955 373.914 373.892 0.199 0.272 
0.275 -0.023 PRE
244.9375 2005 09 01 22 2.6 9.5 17.8 374.734 374.699 374.597 0.512 0.305 
0.42 -0.102 PRE
244.97917 2005 09 01 23 2.6 9.5 17.8 375.889 376.624 375.095 0.968 3.023 
0.257 -1.529 PRE
245.02083 2005 09 02 00 2.6 9.5 17.8 383.539 377.323 376.664 3.434 0.363 
0.535 -0.658 PRE
245.0625 2005 09 02 01 2.6 9.5 17.8 404.529 396.357 391.17 4.293 8.426 
9.43 -5.187 PRE
245.10417 2005 09 02 02 2.6 9.5 17.8 419.268 409.692 400.793 5.609 2.012 
1.856 -8.899 PRE
245.14583 2005 09 02 03 2.6 9.5 17.8 418.503 403.053 396.932 4.163 2.639 
2.164 -6.121 PRE
245.1875 2005 09 02 04 2.6 9.5 17.8 416.242 403.211 398.815 4.174 4.169 
2.325 -4.396 PRE
245.22917 2005 09 02 05 2.6 9.5 17.8 418.22 408.339 400.995 3.671 2.471 
2.831 -7.343 PRE
245.27083 2005 09 02 06 2.6 9.5 17.8 420.275 406.998 398.091 2.467 4.558 
3.799 -8.908 PRE
245.3125 2005 09 02 07 2.6 9.5 17.8 417.073 407.904 402.422 2.717 2.132 
2.391 -5.482 PRE
245.35417 2005 09 02 08 2.6 9.5 17.8 414.63 403.795 400.48 4.526 3.064 
2.107 -3.315 PRE
245.39583 2005 09 02 09 2.6 9.5 17.8 416.399 404.625 397.153 6.47 4.256 
3.132 -7.472 PRE
245.4375 2005 09 02 10 2.6 9.5 17.8 417.079 408.685 403.236 5.573 2.807 
4.058 -5.449 PRE
245.47917 2005 09 02 11 2.6 9.5 17.8 420.808 412.187 406.455 1.606 3.447 
2.37 -5.732 PRE
245.52083 2005 09 02 12 2.6 9.5 17.8 420.05 410.59 404.307 3.128 5.356 
2.849 -6.283 PRE
245.5625 2005 09 02 13 2.6 9.5 17.8 412.6 401.255 395.029 7.586 6.056 
3.897 -6.225 PRE
245.60417 2005 09 02 14 2.6 9.5 17.8 409.137 392.559 388.098 14.58 11.55 
6.646 -4.461 PRE
245.64583 2005 09 02 15 2.6 9.5 17.8 378.641 377.914 378.87 1.636 0.679 
1.116 0.955 PRE
245.6875 2005 09 02 16 2.6 9.5 17.8 378.776 378.891 378.697 1.153 1.185 
1.39 -0.195 PRE
245.72917 2005 09 02 17 2.6 9.5 17.8 374.322 374.281 374.45 0.507 0.507 
0.408 0.169 PRE
245.77083 2005 09 02 18 2.6 9.5 17.8 374.084 374.086 374.069 0.132 0.229 
0.147 -0.017 PRE
245.8125 2005 09 02 19 2.6 9.5 17.8 374.113 374.103 374.295 0.33 0.229 
0.181 0.192 PRE
245.85417 2005 09 02 20 2.6 9.5 17.8 374.468 374.299 374.264 0.315 0.225 
0.209 -0.035 PRE
245.89583 2005 09 02 21 2.6 9.5 17.8 374.389 374.258 374.284 0.2 0.213 
0.206 0.026 PRE
245.9375 2005 09 02 22 2.6 9.5 17.8 374.726 374.577 374.524 0.404 0.271 
0.166 -0.054 PRE
245.97917 2005 09 02 23 2.6 9.5 17.8 374.829 374.946 374.563 0.543 1.107 
0.429 -0.383 PRE

I would like to obtain the hourly (named "hr" above) average of co23 - e.g.

for all years (the dataset actually extends from 2005 - present), all 
months and all days - i would like to get an average of the diurnal cycle.
preferably the result would look something akin to this:

hour   co23(avg)
0        395.345 (e.g.)
1        and so on....
2      
3
4
5
6
7
8
9
10
..
..
23


I have tried for loops, but I can't seem to get that to work and for the 
past 1.5 days I have been trying to use "aggregate" but i can only seem 
to get an average of all variables (across the rows).

Any suggestions would be very much appreciated!

s.heck