  The stellar magnetic field plays a crucial role in the star internal
mechanisms, as in the interactions with its environment. The study of starspots
provides information about the stellar magnetic field, and can characterise the
cycle. Moreover, the analysis of solar-type stars is also useful to shed light
onto the origin of the solar magnetic field. The objective of this work is to
characterise the magnetic activity of stars. Here, we studied two solar-type
stars Kepler-17 and Kepler-63 using two methods to estimate the magnetic cycle
length. The first one characterises the spots (radius, intensity, and location)
by fitting the small variations in the light curve of a star caused by the
occultation of a spot during a planetary transit. This approach yields the
number of spots present in the stellar surface and the flux deficit subtracted
from the star by their presence during each transit. The second method
estimates the activity from the excess in the residuals of the transit
lightcurves. This excess is obtained by subtracting a spotless model transit
from the lightcurve, and then integrating all the residuals during the transit.
The presence of long term periodicity is estimated in both time series. With
the first method, we obtained $P_{\rm cycle}$ = 1.12 $\pm$ 0.16 yr (Kepler-17)
and $P_{\rm cycle}$ = 1.27 $\pm$ 0.16 yr (Kepler-63), and for the second
approach the values are 1.35 $\pm$ 0.27 yr and 1.27 $\pm$ 0.12 yr,
respectively. The results of both methods agree with each other and confirm
their robustness.
