I have 4 data frames consisting of data that looks like this (HuL1 is a bone):
CEMETERY SEX CONTEXT HuL1.L HuL1.R DIRECTIONAL.ASYMMETRY
1 Medieval FEMALE 7172 285 286 0.3508772
2 Medieval FEMALE 8117 316 320 1.2658228
3 Medieval FEMALE 11090 309 312 0.9708738
14 Medieval FEMALE 19 326 332 1.8404908
15 Medieval FEMALE 349 310 313 0.9677419
16 Medieval FEMALE 383 319 322 0.9404389
and
CEMETERY SEX CONTEXT HuL1.L HuL1.R DIRECTIONAL.ASYMMETRY
43 Post-Medieval MALE 20 317 321 1.2618297
44 Post-Medieval MALE 35 334 332 -0.5988024
45 Post-Medieval MALE 47 328 334 1.8292683
46 Post-Medieval MALE 143 332 332 0.0000000
47 Post-Medieval MALE 147 351 354 0.8547009
Each dataframe is a different length, and 2 consist of 'Medieval' data whilst the other 2 are 'Post-Medieval (A = medieval female data, B= medieval male data, C = post-medieval female data, D = post-medieval male data). I have made a boxplot using
x=boxplot(A$DIRECTIONAL.ASYMMETRY,B$DIRECTIONAL.ASYMMETRY,
C$DIRECTIONAL.ASYMMETRY
,D$DIRECTIONAL.ASYMMETRY,xlab="PERIOD",ylab="DIRECTIONAL ASYMMETRY
(%)",names=c("Medieval","Medieval","Post-Medieval","Post-
Medieval"),col=c("turquoise","red","turquoise","red"))
legend(x="topleft",title="Sex",c("Female","Male"),fill=c("turquoise","red"))
but I want the 'Medieval' and 'Post-Medieval' plots to be grouped together, so the x-axis only says Medieval and Post-Medieval once.