R-helpers:

 I am experiencing some odd behavior with the 'matrix' function that I have
not experienced before and was wondering if there is something that I was
missing in my code.

 ---------------------------------
 > sessionInfo()
R version 2.6.1 (2007-11-26)
i386-pc-mingw32
 locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
 attached base packages:
[1] splines   grid      stats     graphics  grDevices utils     datasets
 methods
[9] base
 other attached packages:
[1] meta_0.8-2         car_1.2-7          arm_1.1-1          R2WinBUGS_2.1-6

[5] coda_0.13-1        lme4_0.99875-9     Matrix_0.999375-3  nlme_3.1-86

[9] latticeExtra_0.3-1 RColorBrewer_1.0-2 survival_2.34      MASS_7.2-39

[13] foreign_0.8-23     RGraphics_1.0-6    lattice_0.17-4
 loaded via a namespace (and not attached):
[1] rcompgen_0.1-17 tools_2.6.1

 > rm(list=ls())

> matrix(c(7,47,4,38,20,96,1,14,10,48,2,101,12,161,     # Make a data matrix
+ 1,28,1,19,22,49,25,162,31,200,9,39,22,193,
+ 0.5,45.5,31,131,4,75,31,220,7,55,3,91,14.5,
+ 25.5,3,65,25,54,24,41,37,95,11,17,26,49,13,
+ 84,38,170,29,60,9,20,44,47,30,160,40,185,10,
+ 41,40,185,4.5,46.5,60,140,12,75,42,225,26,57,
+ 17,92,23.5,23.5,6,68), ncol=2, byrow=T)

     [,1] [,2]
[1,]  7.0   47
[2,]  4.0   38
[3,] 20.0   96
[4,]  1.0   14
[5,] 10.0   48
[6,]  2.0  101
[7,] 12.0  161
[8,]  1.0   28
[9,]  1.0   19
[10,] 22.0   49
[11,] 25.0  162
[12,] 31.0  200
[13,]  9.0   39
[14,] 22.0  193
[15,]  0.5   46
[16,] 31.0  131
[17,]  4.0   75
[18,] 31.0  220
[19,]  7.0   55
[20,]  3.0   91
[21,] 14.5   26
[22,]  3.0   65
[23,] 25.0   54
[24,] 24.0   41
[25,] 37.0   95
[26,] 11.0   17
[27,] 26.0   49
[28,] 13.0   84
[29,] 38.0  170
[30,] 29.0   60
[31,]  9.0   20
[32,] 44.0   47
[33,] 30.0  160
[34,] 40.0  185
[35,] 10.0   41
[36,] 40.0  185
[37,]  4.5   46
[38,] 60.0  140
[39,] 12.0   75
[40,] 42.0  225
[41,] 26.0   57
[42,] 17.0   92
[43,] 23.5   24
[44,]  6.0   68

------------------------------------

Note the problems in rows 15, 21, 37 and 43.  They should read [0.5, 45.5],
[14.5, 21.5], etc...  The matrix function seems to be rounding the second
column up to the next integer.  Why would this occur?  Can I do something to
prevent this?

I would very much appreciate any comments.

Thanks,

Brant Inman
Mayo Clinic

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