Clear [x] f1[x_] := x f2[x_] := Exp[-x] f3[x_] := 1/(1+x^2) f4[x_] := 1/(1+x^4) Fit[{ {0.1 ,1.0}, {1 ,0.65}, { 11 , 0.4000}, { 21 , 0.2200}, { 29 , 0.200 } , { 35 , 0.18 }, { 50 , 0.15}, { 100 , 0.1} }, { 1,f1[x],f2[x],f3[x] },{x}] Print[" 1 s b"] For [x:=0.1, x< 4, x+=0.2 , { Print [ { x, F1s[x]//N }] }] Clear [x] f1[x_] := 1/(70+x) f2[x_] := Exp[-x 0.1] f3[x_] := 1/(50+x^2) f4[x_] := 1/(200+x^2) llist:= { {1.00 , 0.935000 }, { 5.00 , 0.75 }, { 10.00 , 0.55 }, { 15.00 , 0.52 }, { 20.00 , 0.42 }, { 25 , 0.3055 }, { 35.00 , 0.21 }, { 50.00 , 0.115 }, {70.00 , 0.08 }, { 100.0 , 0.16 } } Fit[llist,{ 1,f1[x],f3[x],f4[x] },{x}]