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We studied the correlation between brightness and polarization variations in3C~279 at different wavelengths, over time intervals long enough to cover thetime lags due to opacity effects. We used these correlations together with VLBIimages to constrain the radio and high energy source position.We made 7 mmradio continuum and $R$-band polarimetric observations of 3C~279 between 2009and 2014. The radio observations were performed at the Itapetinga RadioObservatory, while the polarimetric data were obtained at Pico dos DiasObservatory, both in Brazil. We compared our observations with the $\gamma$-rayFermi/LAT and $R$-band SMARTS light curves. We found a good correlation between7~mm and $R$-band light curves, with a delay of $170 \pm 30$ days in radio, butno correlation with the $\gamma$ rays. However, a group of several $\gamma$-rayflares in April 2011 could be associated with the start of the 7 mm strongactivity observed at the end of 2011.We also detected an increase in $R$-bandpolarization degree and rotation of the polarization angle simultaneous withthese flares. Contemporaneous VLBI images at the same radio frequency show twonew strong components close to the core, ejected in directions very differentfrom that of the jet.The good correlation between radio and $R$-bandvariability suggests that their origin is synchrotron radiation. The lack ofcorrelation with $\gamma$-rays produced by the Inverse Compton process on someoccasions could be due to the lack of low energy photons in the jet directionor to absorption of the high energy photons by the broad line region clouds.The variability of the polarization parameters during flares can be easilyexplained by the combination of the jet polarization parameters and those ofnewly formed jet components.

Multiwavelength analysis of brightness variations of 3C~279: Probing the relativistic jet structure and its evolution