r - Grouped multiplication of matrices with unequal dimensions -

i new r , trying determine how can following:

i have 2 matrices, each row date , each column number. second matrix longer first. want create function multiply first row (say january number) first 4 rows of second matrix (which january numbers well). so, i'm looking 4 results. want move second row of first matrix (february number) , multiply 4 february numbers second matrix. eventually, hoping code multiply first second if month , years match.

first matrix

jan 2007        143.75 feb 2007        140.93 

second matrix

2007-01-05         12.14 2007-01-12         10.15 2007-01-19         10.40 2007-01-26         11.13 2007-02-02         10.08 2007-02-09         11.10 2007-02-16         10.02 2007-02-23         10.58 

assuming both matrices, , dates on left row names, can try along these lines. here match months of row names of 2 matrices , use create vector calculation.

idx <- match(format(as.date(rownames(m2)), "%b"), sub(" .*", "", rownames(m1))) m2 * m1[idx] #                [,1] # 2007-01-05 1745.125 # 2007-01-12 1459.062 # 2007-01-19 1495.000 # 2007-01-26 1599.938 # 2007-02-02 1420.574 # 2007-02-09 1564.323 # 2007-02-16 1412.119 # 2007-02-23 1491.039 

data:

m1 <- structure(c(143.75, 140.93), .dim = c(2l, 1l), .dimnames = list(     c("jan 2007", "feb 2007"), null)) m2 <- structure(c(12.14, 10.15, 10.4, 11.13, 10.08, 11.1, 10.02, 10.58 ), .dim = c(8l, 1l), .dimnames = list(c("2007-01-05", "2007-01-12",  "2007-01-19", "2007-01-26", "2007-02-02", "2007-02-09", "2007-02-16",  "2007-02-23"), null)) 

note: haven't given information in post, whether or not doing multiple years, whether dates row names or columns, etc. if doing multiple years, please post more representative data example desired result.