anscombe_concat = {
const t1 = anscombe_raw.select({x1:'x',y1:'y'}).derive({set:1});
const t2 = anscombe_raw.select({x2:'x',y2:'y'}).derive({set:2});
const t3 = anscombe_raw.select({x3:'x',y3:'y'}).derive({set:3});
const t4 = anscombe_raw.select({x4:'x',y4:'y'}).derive({set:4});
const t1234 = t1.concat([t2,t3,t4])
.derive({sample:d=>op.row_number()},{before:0})
.relocate('set',{before:1})
return t1234;
}