  The evolution of stellar disks is of great importance for understanding many
aspects of galaxy formation. In this work we perform stellar population
synthesis on radially resolved photometry of 564 disk galaxies from the SDSS
DR5, selected to have both spectra of the central regions and photometry. To
explore fully the multi-dimensional likelihood space defined by the output
parameters of the spectral synthesis, we use Markov Chain Monte Carlo to
quantify the expectation values, the uncertainties and the degeneracies of the
parameters. We find good agreement between the parameter values obtained using
the SDSS broad-band colors and the spectra respectively. In general the derived
mean stellar age and the best-fit stellar metallicity decline in value from the
galaxy center to the outer regions (around 1.5 half-light radii), based on
sub-samples defined by concentration index. We also find that the radial
dependency of the stellar population parameters exhibits a significant
variation, and this diversity is likely related to morphology and the physics
of star formation.
