High-mass slope, α_IMF, of the IMF versus galactocentric radius, R_gc, for each open cluster. The clusters are coloured by their metallicity [Fe/H] and categorised into four age groups. Error bars are the upper and lower bounds of the inferred parameter from the MCMC algorithm. The dashed line is the mean trend of the whole sample, and the shaded region denotes one σ from this trend. The α_IMF trend is $\frac{\mathrm{\Delta }{\alpha }_{\text{IMF}}}{\mathrm{\Delta }{R}_{gc}}=-0.020\pm 0.011$ per kpc.