[R] Problem with predict.lm()

Wed Apr 29 16:56:26 CEST 2015

Dear Arnab,

Thank you very much for your reply. It does not give an error message.
The problem is that predict does "work and predict" on the old data and does not make the predictions with the provided new data.

Best,

Martin

Gesendet: Mittwoch, 29. April 2015 um 16:51 Uhr
Von: "ARNAB KR MAITY" <arnab_stat at yahoo.com>
An: "Martin Spindler" <Martin.Spindler at gmx.de>, "r-help at r-project.org" <r-help at r-project.org>
Betreff: Re: [R] Problem with predict.lm()

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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