set T ordered;
param s{T};
...
file.data
set T := 1..257;
param: s := 255.94 258.63 258.89 261.07 243.40 247.49 245.42 245.81 245.88 252.05 251.88 249.32 242.63 243.14 246.50 252.17 249.57 249.38 253.29 257.07 255.04 255.57 252.21 252.21 250.96 249.10 251.72 256.66 255.95 257.63 259.83 259.21 257.91 261.61 265.64 265.02 264.43 261.58 262.46 267.82 267.22 267.98 267.88 267.30 267.38 269.43 269.06 263.84 264.94 266.37 266.13 268.65 271.22 271.12 268.74 268.84 268.91 263.35 258.51 258.06 260.07 258.07 258.89 256.09 258.51 265.49 266.16 269.43 270.16 271.37 271.57 259.75 259.77 259.21 257.92 256.13 256.42 260.14 262.46 263.93 263.80 262.61 261.33 261.56 263.00 260.32 258.79 257.48 256.54 257.62 253.31 253.85 256.78 258.71 255.39 251.35 252.57 253.02 250.83 253.51 253.76 254.63 253.42 262.16 266.69 265.33 266.45 267.05 265.17 271.52 270.20 271.26 271.43 274.30 274.45 269.77 270.68 268.94 271.67 275.66 274.82 273.78 269.06 272.31 270.98 273.50 271.78 275.81 272.02 271.78 270.02 270.55 267.85 269.32 270.26 272.05 270.51 268.47 270.00 266.66 263.50 264.68 265.19 262.50 266.02 272.02 272.21 272.06 272.98 271.93 271.15 269.98 266.49 261.90 262.75 262.55 258.69 260.56 260.77 261.03 260.24 256.98 257.09 261.13 259.18 259.68 262.33 262.51 261.52 258.35 264.48 265.59 265.87 265.88 266.84 266.47 267.43 269.31 268.13 270.65 268.82 269.73 270.16 269.18 269.76 268.88 268.26 269.08 272.59 271.91 271.38 270.62 271.86 272.39 278.07 278.24 277.93 273.98 275.22 275.50 276.41 279.38 276.97 282.88 283.66 282.28 282.38 281.38 277.28 278.53 278.97 279.06 279.06 279.20 276.31 273.93 275.15 273.33 273.69 267.92 267.72 268.34 263.82 264.60 266.47 266.22 267.21 269.00 267.23 268.64 270.91 273.70 272.49 271.81 274.93 277.59 278.13 276.57 277.03 276.52 276.31 275.31 274.28 276.29 278.91 277.47 277.38 276.87 277.87 276.83 277.08 279.40 277.72 275.31 279.43 280.01 280.67;
the idea is to initialise of set the values of s up.