Get rid of \\addlinespace in kable
In a knitr/Sweave report, the kable function of knitr with the option booktabs=TRUE adds a \addlinespace each fifth line: P1 & A & 10 & 11.016181 & 110.16181 & 44.95101 & 269.9745\\ P1 & B & 10 & 8.592386 & 85.92386 & 35.06083 & 210.5743\\ P1 & A & 100 & 120.610305 & 120.61031 & 58.61274 & 248.1857\\ P1 & B & 100 & 94.990728 & 94.99073 & 46.16245 & 195.4671\\ P2 & A & 1000 & 698.097191 & 69.80972 & 37.34843 & 130.4846\\ \addlinespace P2 & B & 1000 & 837.649249 & 83.76492 & 44.81452 & 156.5690\\ P2 & A & 10000 & 10356.365176 & 103.56365 & 49.47422 & 216.7883\\ P2 & B & 10000 & 10214.989594 &