Hello -
Keld Jørn Simonsen wrote:
Hi
I have a problem with lm and predict
I have
us
[1] 2789.53 3128.43 3255.03 3536.68 3933.18 4220.25 4462.83 4739.48
[9] 5103.75 5484.35 5803.08 5995.93 6337.75 6657.40 7072.23 7397.65
[17] 7816.83 8304.33 8746.98 9268.43 9816.98 10127.95 10469.60 10960.75
[25] 11685.93 12433.93 13194.70 13843.83
us.p
[1] 227.62 229.92 232.13 234.25 236.31 238.42 240.59 242.75 244.97 247.29
[11] 250.05 253.39 256.78 260.15 263.33 266.46 269.58 272.82 276.02 279.20
[21] 282.31 285.25 288.10 290.85 293.53 296.26 299.08 301.97
us.l = lm(log(us) ~ log(us.p))
predict(us.l,n.ahead=5)
1 2 3 4 5 6 7 8
8.079754 8.131908 8.181531 8.228692 8.274111 8.320224 8.367224 8.413588
9 10 11 12 13 14 15 16
8.460813 8.509709 8.567285 8.636117 8.705057 8.772694 8.835719 8.897015
17 18 19 20 21 22 23 24
8.957402 9.019376 9.079867 9.139289 9.196752 9.250495 9.302067 9.351347
25 26 27 28
9.398927 9.446950 9.496094 9.545979
Why does predict not give me any predictions? The result of predict() is
same lenght (28) as the us and us.p variables.
The version of 'predict' being called on 'us.l' (i.e., predict.lm) is
doing predictions, and it should be giving you a result of identical
length as your original vectors. What are you expecting here? Your
usage of the 'n.ahead' parameter suggests to me you might be wanting to
fit your model using a different function than 'lm', and use its
corresponding prediction function.
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