maples2003 = maples
.map((d) => ({
year: parseInt(d.Year),
watershed: d.Watershed,
stemLength: parseFloat(d.StemLength),
leafMass: parseFloat(d.LeafDryMass),
stemMass: parseFloat(d.StemDryMass),
leafArea: parseFloat(d.CorrectedLeafArea)
}))
.filter((d) => d.year === 2003)