Referencing entries of matrix in R within for loop

问题

Is there a way to reference a part of a matrix within a for loop?

for (j in 1:x1)
  for (k in 1:x2) {
    matrix[j,8k-6:8k+1] <- AlleleFreq.t1[k,1:8]      
   }
}

I get an error message saying "unexpected symbol in "alldata.t1[j,8k". What is the correct syntax for preforming this sort of operation?

Thank you.

回答1:

use parens & * to multiply:

 8k-6:8k+1   ~~~>  (8*k-6):(8*k+1)

---

the seq operator : takes precedence over arithmetic operators such as - Thus, without parens, you have

(8*k) - c(6, 7, 8) + ((8*k) + 1)

来源：https://stackoverflow.com/questions/20553057/referencing-entries-of-matrix-in-r-within-for-loop