各位前辈，想请教一下如何将同一公司(num)相同年份(year)发行的债券期限(term)按发行规模（total）进行加权平均？感谢。把相同年份的数据归为一年，多余的删除。然后将相同年份的发行金额叠加。
num total term rate year
27 20 1 .0535 08apr2014
27 20 .7397 .049 28jul2014
27 20 .7397 .046 13oct2014
27 40 .7397 .048 01apr2015
27 35 1 .0388 18jun2015
27 60 5 .039 27nov2015
27 30 .7397 .0295 01jun2016
27 30 .7397 .0425 22feb2017
27 30 1 .0438 08mar2017
27 10 .7397 .0441 19jul2017
27 30 .7397 .0499 13nov2017
27 12 5 .0525 20nov2017
27 8 3 .052 20nov2017
27 10 5 .0525 22nov2017
27 25 .1644 .0455 02mar2018
27 10 .1643 .044 29mar2018
27 10 .1644 .039 09apr2018
27 15 .1644 .0365 12apr2018
27 10 .7397 .045 22may2018
27 20 5 .048 23may2018
27 25 .7397 .0465 06jun2018
27 30 .7397 .035 01aug2018
27 30 3 .0465 29nov2018
27 10 .3288 .0305 22jan2019
27 10 .3288 .0305 24jan2019
27 16.5 10 .0405 22feb2019
27 16.5 10 .0405 22feb2019
27 30 .4918 .03 17apr2019
27 20 .3279 .0309 16may2019
27 11.5 10 .0415 24jun2019
27 11.5 10 .0415 24jun2019
27 30 3 .0395 27aug2019
27 10 .2732 .025 03sep2019
27 10 .2732 .025 03sep2019
27 30 .4918 .0309 09oct2019
27 20 .2459 .0205 06dec2019
27 20 .4918 .021 23dec2019
88 3 5 .0312 19oct2016
90 18 3 .0596 20dec2018
421 3 1 .0354 20oct2015
428 1 .7397 .062 30mar2017
429 10 5 .0679 12oct2011
429 6.8 5 .04 27feb2019
488 5 3 .065 09aug2019
514 3.3 5 .044 30nov2016
544 5 3 .0452 19dec2018
544 5 3 .0428 25jun2019
598 11 5 .0549 16sep2014
598 2 .4932 .05 14jan2015
598 1 .4932 .051 08apr2015
598 1 .4932 .051 08apr2015
598 9 .7377 .0339 05aug2015
598 11 5 .0295 28jul2016
598 5 .7397 .0293 21oct2016
598 3 3 .049 19oct2017
598 5 5 .041 27nov2018
598 8 5 .0426 25apr2019
598 8 5 .0426 25apr2019
598 10 5 .0358 26nov2019
598 10 5 .0358 26nov2019
600 4.5 6 .062 29aug2011
600 10 1 .052 25dec2014