2 fixed typo edited Oct 16 '15 at 23:21 rhuairahrighairidh 12144 bronze badges If it's a one off kind of thing then I find just rewriting the values in the list easier. listofspectra = {{{x1,y1},{x2,y2},{x3,y3}},{{a1,b1},{a2,b2},{a3,b3}}}; listofspectra[[1, All, 2]] = listofspectra[[1, All, 2]]/3  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1}, {a2, b2}, {a3, b3}}} listofspectra[[1listofspectra[[2, All, 2]] = listofspectra[[1listofspectra[[2, All, 2]]/5  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1/5}, {a2, b2/5}, {a3, b3/5}}} But the MapThread method in eldo's answer is more general. If it's a one off kind of thing then I find just rewriting the values in the list easier. listofspectra = {{{x1,y1},{x2,y2},{x3,y3}},{{a1,b1},{a2,b2},{a3,b3}}}; listofspectra[[1, All, 2]] = listofspectra[[1, All, 2]]/3  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1}, {a2, b2}, {a3, b3}}} listofspectra[[1, All, 2]] = listofspectra[[1, All, 2]]/5  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1/5}, {a2, b2/5}, {a3, b3/5}}} But the MapThread method in eldo's answer is more general. If it's a one off kind of thing then I find just rewriting the values in the list easier. listofspectra = {{{x1,y1},{x2,y2},{x3,y3}},{{a1,b1},{a2,b2},{a3,b3}}}; listofspectra[[1, All, 2]] = listofspectra[[1, All, 2]]/3  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1}, {a2, b2}, {a3, b3}}} listofspectra[[2, All, 2]] = listofspectra[[2, All, 2]]/5  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1/5}, {a2, b2/5}, {a3, b3/5}}} But the MapThread method in eldo's answer is more general. 1 answered Oct 16 '15 at 20:25 rhuairahrighairidh 12144 bronze badges If it's a one off kind of thing then I find just rewriting the values in the list easier. listofspectra = {{{x1,y1},{x2,y2},{x3,y3}},{{a1,b1},{a2,b2},{a3,b3}}}; listofspectra[[1, All, 2]] = listofspectra[[1, All, 2]]/3  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1}, {a2, b2}, {a3, b3}}} listofspectra[[1, All, 2]] = listofspectra[[1, All, 2]]/5  {{{x1, y1/3}, {x2, y2/3}, {x3, y3/3}}, {{a1, b1/5}, {a2, b2/5}, {a3, b3/5}}} But the MapThread method in eldo's answer is more general.