Hello R users,
I have the following annoying matrix multiplication and I do not know how to
avoid the nested loops, so maybe someone can help me with some ideas. I have
searched the forum for past posts but nothing came up.Here it is:
aa=matrix(1:9,3,3) bb=matrix(seq(10,90,by=10),3,3) cc=matrix(seq(100,900,
by=100),3,3) dd=NULL
for(r in 1:3){ for(c in 1:3){ for(j in 1:3){ for(k in
1:3){dd=c(dd,aa[j,k]*bb[r,j]*cc[k,c])}}}}dd [1] 1000 8000 21000 8000
40000 96000 21000 84000 189000 4000[11] 20000 42000 32000 100000 192000
84000 210000 378000 7000 32000[21] 63000 56000 160000 288000 147000
336000 567000 2000 16000 42000[31] 10000 50000 120000 24000 96000
216000 8000 40000 84000 40000[41] 125000 240000 96000 240000 432000
14000 64000 126000 70000 200000[51] 360000 168000 384000 648000 3000 24000
63000 12000 60000 144000[61] 27000 108000 243000 12000 60000 126000
48000 150000 288000 108000[71] 270000 486000 21000 96000 189000 84000 240000
432000 189000 432000[81] 729000
What I want to obtain is the content of the vector dd in an efficient (fast)
and clever way.Thank you very much and have a great day ahead!Eugen
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
