Compute the monthly stock return for Chevron using ln(P_t/P_t-1) where Pt is current price and Pt-1 is previous price.

monthcomnamprc2010m1CHEVRON72.122010m2CHEVRON72.32010m3CHEVRON75.832010m4CHEVRON81.442010m5CHEVRON73.872010m6CHEVRON67.862010m7CHEVRON76.212010m8CHEVRON74.082010m9CHEVRON81.052010m10CHEVRON82.62010m11CHEVRON80.972010m12CHEVRON91.252011m1CHEVRON94.932011m2CHEVRON103.752011m3CHEVRON107.492011m4CHEVRON109.442011m5CHEVRON104.912011m6CHEVRON102.842011m7CHEVRON104.022011m8CHEVRON98.842011m9CHEVRON92.592011m10CHEVRON105.052011m11CHEVRON102.822011m12CHEVRON106.42012m1CHEVRON103.122012m2CHEVRON109.122012m3CHEVRON107.212012m4CHEVRON106.562012m5CHEVRON98.312012m6CHEVRON105.52012m7CHEVRON109.582012m8CHEVRON112.162012m9CHEVRON116.562012m10CHEVRON110.24072012m11CHEVRON105.692012m12CHEVRON108.142013m1CHEVRON115.152013m2CHEVRON117.152013m3CHEVRON118.822013m4CHEVRON122.012013m5CHEVRON122.752013m6CHEVRON118.342013m7CHEVRON125.892013m8CHEVRON120.432013m9CHEVRON121.52013m10CHEVRON119.962013m11CHEVRON122.442013m12CHEVRON124.912014m1CHEVRON111.632014m2CHEVRON115.332014m3CHEVRON118.912014m4CHEVRON125.522014m5CHEVRON122.792014m6CHEVRON130.552014m7CHEVRON129.242014m8CHEVRON129.452014m9CHEVRON119.322014m10CHEVRON119.952014m11CHEVRON108.872014m12CHEVRON112.182015m1CHEVRON102.532015m2CHEVRON106.682015m3CHEVRON104.982015m4CHEVRON111.062015m5CHEVRON1032015m6CHEVRON96.472015m7CHEVRON88.482015m8CHEVRON80.992015m9CHEVRON78.882015m10CHEVRON90.882015m11CHEVRON91.322015m12CHEVRON89.96