[R] Problem with predict.lm()

Wed Apr 29 16:51:22 CEST 2015

Hi,
It seems to be working in my R. Although it is throwing the warning message
Warning message:'newdata' had 200 rows but variables found have 100 rows 
 y  [1] -1.071307580  0.102414204 -0.965046207  1.386057875  0.726835339  [6] -0.186549950 -0.777144258  1.137210314 -1.069446945 -0.696084338 [11] -0.467686285  0.997316781  0.776265490 -1.385720997 -0.007438381 [16]  0.302821728  0.024075173 -0.590401970  0.877104292  0.652724314 [21]  2.142135078  2.023051454 -0.547221960  0.342600702  0.080848203 [26]  0.074609232  0.255946197 -0.191242759  1.036445108  0.895068954 [31]  0.589477883  0.123230750  1.467210735 -1.636657283 -0.131504288 [36] -0.665000122  0.390977868  0.546802014  0.445498091  1.063872749 [41]  1.406788635 -0.037147550 -1.047190960 -0.189105987  0.069617165 [46] -0.049760285 -1.454279226  0.358351554  0.246587937 -0.060735329 [51]  1.664530111 -0.475931484  0.405480604  1.560446941 -0.030537155 [56] -1.060319583 -1.828624216 -0.429391165  0.301697744 -0.029593593 [61] -1.696307754  0.342678986 -0.433965195 -0.947338037  0.318186677 [66]  0.539630789 -1.354555193  0.086168702  0.002950100  1.783486665 [71] -1.182419158 -0.930524123  0.376579158 -1.085035387  1.186125702 [76]  0.719738391 -0.486692820 -2.105396602  0.531238276  1.302812739 [81]  0.347851244  0.016452693  0.417535566  0.277705766  2.286275977 [86]  1.610183518  2.032037030  1.319074179  1.129375593  0.176684807 [91] -0.630517144  1.302785450  0.994275267 -0.060116993 -0.655966924 [96]  1.628197169  1.935532651 -1.635783346 -1.172511179  1.238336597> ynew           1            2            3            4            5            6 -0.270916637  0.169149841  0.191348061 -0.009541999  0.112027155  0.016242323            7            8            9           10           11           12 -0.062178365  0.275322344  0.397030485  0.565078468  0.301230303  0.305405674           13           14           15           16           17           18  0.552136794 -0.151275710  0.470280882  0.349631748  0.022005869  0.181384646           19           20           21           22           23           24  0.143719339  0.478791323  0.518731127  0.229860133 -0.199433324  0.310576455           25           26           27           28           29           30  0.127612633 -0.157347145  0.413807523  0.007961485 -0.288867750  0.208759771           31           32           33           34           35           36  0.286165027  0.299492579  0.197312294  0.135601904  0.452828662  0.187191405           37           38           39           40           41           42  0.335596502 -0.109960231 -0.303770506 -0.276385255  0.429700474  0.003930969           43           44           45           46           47           48  0.184186301  0.140858190  0.479882236  0.182523553 -0.133845870  0.443940376           49           50           51           52           53           54  0.070571673 -0.383780163  0.362153269  0.202527841  0.164299813  0.327998904           55           56           57           58           59           60  0.047612361 -0.032167295  0.060976285  0.231929803 -0.449532973  0.109925656           61           62           63           64           65           66  0.468842330  0.108507841  0.158697337 -0.125813680  0.501159861  0.101646132           67           68           69           70           71           72  0.194383106 -0.006185569  0.354467348  0.340013811  0.088757961  0.439984356           73           74           75           76           77           78  0.330976669  0.449337326  0.081841142 -0.190123754  0.337794560 -0.111895039           79           80           81           82           83           84  0.598231564  0.444399789  0.388313945  0.244270482  0.200026237  0.009025077           85           86           87           88           89           90  0.341093767 -0.164196034  0.825849472  0.325975911  0.494473323  0.270037159           91           92           93           94           95           96  0.369787280  0.247455471  0.282701738 -0.541688411 -0.145796547  0.073172268           97           98           99          100  0.685833173 -0.079174316 -0.193161949 -0.137517175 
 Arnab Kumar Maity
Graduate Teaching Assistant
Division of Statistics
Northern Illinois University
DeKalb,
Illinois 60115
U.S.A
      From: Martin Spindler <Martin.Spindler at gmx.de>
 To: r-help at r-project.org 
 Sent: Wednesday, April 29, 2015 9:21 AM
 Subject: [R] Problem with predict.lm()

Dear all,

the following example somehow uses the "old data" (X) to make the predictions, but not the new data Xnew as intended.

y <- rnorm(100)
X <- matrix(rnorm(100*10), ncol=10)
lm <- lm(y~X)
Xnew <- matrix(rnorm(100*20), ncol=10)
ynew <- predict(lm, newdata=as.data.frame(Xnew)) #prediction in not made for Xnew

How can I foce predict.lm to use use the new data?

Thank you very much for your efforts in advance!

Best,

Martin

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