import graph;
unitsize(1cm);

ylimits(min=-3,max=4);

yaxis(Label("$y_1$",align=E),
      RightTicks(new real[]{0,1,1.5},Size=1mm,1bp+red),
      Arrow);

yaxis(axis=XEquals(2.2),"$y_2$",
      Ticks(),
      Arrow);

yaxis(axis=XEquals(4.4),"$y_3$",
      ymin=-2,ymax=1.5,red,
      Ticks(end=false),
      Arrow);

yaxis(axis=XEquals(6.6),"$y_4$",
      ymax=3,
      RightTicks(Step=3,step=.5,endlabel=false),
      Arrow);

shipout(bbox(2mm,Fill(white)));