gno/usr.bin/awk/tests/sum3

# sum3 - print sums of numeric columns
#     input:  rows of integers and strings
#     output: sums of numeric columns
#       assumes every line has same layout

NR==1 { nfld = NF
        for (i = 1; i <= NF; i++)
            numcol[i] = isnum($i)
      }

      { for (i = 1; i <= NF; i++)
            if (numcol[i])
                sum[i] += $i
      }

END   { for (i = 1; i <= nfld; i++) {
            if (numcol[i])
                printf("%g", sum[i])
            else
                printf("--")
            printf(i < nfld ? "\t" : "\n")
        }
      }

function isnum(n) { return n ~ /^[+-]?[0-9]+$/ }