First the data are imported from *.xls files.
After that these graphs can be generated.
fig=ggplot(data=df, aes(x,y,colour=z))+
geom_point()
print(fig)
fig=ggplot(data=df, aes(x,y,size=z))+
geom_point()
print(fig)
fig=ggplot(data=df, aes(x,y,size=z, colour=z))+
geom_point()
print(fig)