Find the values that let me split x in equally numbered groups

Question

I have some data:

x <- c(0.0636931012704989, 0.0421033586843369, 0.0214721845269228, 
0.038624779052474, 0.033235347720021, 0.0307709640052774, 0.0606316442337883, 
0.0289958997354256, 0.0573689255248752, 0.044448618126441, 0.0164384406368751, 
0.0357802024114138, 0.0133831663454831, 0.0329126088838874, 0.051468481535772, 
0.0302927520748979, 0.169023097551101, 0.0311182034472608, 0.117954563949638, 
0.0593735124639249, 0.0110273691186214, 0.0286868155187407, 0.0522496344459376, 
0.0298854332250777, 0.0626024185545931, 0.106914814257457, 0.0396392209572767, 
0.0111988702332617, 0.0276848766950444, 0.0142151606082234)

I would like to find the values, in R preferably, in order to split x equally numbered groups.

Answer 1

Use the quantiles:

ngroups <- 3
q <- quantile(x, 0:ngroups/ngroups)
sprintf("The boundaries of the %d groups are: %s", groups, paste(signif(q, 3), collapse=", "))
# Or simply:
q

You can then cut:

cut.x <- cut(x, breaks=q, include.lowest=TRUE)
table(cut.x)
# Or split if you want to keep the exact numeric values:
split(x, cut.x)