I realized that I totally forgot about the fact that there are
mismatch probes on the HG-U133 Plus 2.0 arrays which explains why
there are x2 the number of probes for each probeset.  For those
interested in just grabbing the pm probes, you can do something like
this:

ps <- "1053_at"
types <- "pm
cells <- lapply(types, FUN=function(type) identifyCells(cdf,
types=type))
names(cells) <- types
pm_cells <- unlist(cells["pm"])
probe_cells <- getCellIndices(cdf, units=indexOf(cdf, names=ps),
unlist=TRUE)
probe_cells <- intersect(pm_cells, probe_cells) #retrieves only the PM
probes

This will return just the probe_cells of PM probes.  And then you can
use:

m <- getIntensities(cs, indices=probe_cells)

To get the intensities of just those probes.

Fong

On Dec 21, 11:36 am, Fong <fongchunc...@gmail.com> wrote:
> Hi all,
>
> I've been looking at probe-level data for HG-U133 Plus 2.0 arrays and
> following the tutorial listed at "http://groups.google.com/group/aroma-
> affymetrix/web/data-affymetrixcelset-object".  When I run the
> readUnits(csOrig,unit=1) #gets the first unit (aka probeset), where
> csOrig is a celSet for HG-U133 Plus 2.0 arrays, I am getting a higher
> than expected number of probes grouped to this probeset.  In this
> case, unit=1 is the probeset "AFFX-BioB-5_at", and it reports as
> having 40 probes:
>
> Here is the output:
>
> readUnits(cs, unit=1)
> $`AFFX-BioB-5_at`
> $`AFFX-BioB-5_at`$`AFFX-BioB-5_at`
> $`AFFX-BioB-5_at`$`AFFX-BioB-5_at`$intensities
>       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,
> 13]
>  [1,]  391  286  384  477  407  405  328  506  402   344   344   348
> 377
>  [2,]   89   81   92  119  116  103   92   99  113   100    84
> 89    96
>  [3,]  198  171  254  256  233  209  181  259  248   214   164   153
> 223
>  [4,]   68   87   86   97   89   84   78   63   89    79    80
> 68    81
>  [5,]  647  634  698  727  698  656  600  905  701   731   656   733
> 805
>  [6,]  166  172  177  220  205  163  190  228  214   221   229   179
> 175
>  [7,]  148  117  144  200  153  112  107  165  155   152   137   124
> 164
>  [8,]  105   86   86   93   84   74   77   80   78    86    88
> 85    60
>  [9,]  507  511  561  619  520  499  532  715  661   621   539   596
> 600
> [10,]  487  247  316  380  344  400  268  374  449   393   364   278
> 375
> [11,]  650  559  688  672  690  619  665  836  793   679   679   729
> 793
> [12,]  203  161  260  229  233  194  201  269  260   234   189   222
> 225
> [13,] 1046  862 1174 1175 1054  998  974 1318 1145  1057  1119  1150
> 1356
> [14,]  502  436  566  566  509  501  432  603  522   514   507   510
> 583
> [15,] 1022  863 1152 1167 1143 1021  963 1308 1145  1152  1166  1134
> 1399
> [16,]  302  218  301  355  346  268  249  386  317   326   275   272
> 398
> [17,]  894  744 1020 1070  858  858  794 1181  959   991   870  1025
> 1166
> [18,]  243  208  303  289  261  257  255  259  273   290   221   228
> 313
> [19,]  382  337  470  381  369  373  383  520  455   384   415   425
> 447
> [20,]  104  109  113  147  140  120  119  127  128   136   129    96
> 110
> [21,]  462  332  427  428  389  411  343  545  539   449   419   463
> 504
> [22,]  156  145  137  169  141  166  147  146  164   171   169   134
> 129
> [23,]  238  148  246  252  249  215  190  281  209   198   191   203
> 201
> [24,]   89   93   80  106  122   89   90   85   89    93    92
> 87    88
> [25,]  240  201  331  246  230  249  180  277  252   250   265   222
> 286
> [26,]  109   96  103  147  109  117   89   88   95   113   113
> 77    85
> [27,]  160  163  176  178  163  205  158  170  180   163   162   168
> 204
> [28,]   97   91  102  155  116  142  104  101   97   104   102
> 80    90
> [29,]  614  532  623  628  576  564  550  701  575   623   570   485
> 689
> [30,]  114   82   99   93  118  109   94  105  114    90    91
> 86    97
> [31,]  179  168  147  165  200  169  133  173  169   146   145   148
> 140
> [32,]  614  458  459  612  846  551  497  800  805   611   508   383
> 454
> [33,]  305  330  346  339  300  297  322  375  383   394   355   326
> 369
> [34,]  116  127  127  146  170  131  137  140  139   129   141   122
> 124
> [35,]  145  127  167  164  174  148  167  160  188   190   153   151
> 170
> [36,]  114   80  100  128  148  102  121   97  105   135   100
> 89    89
> [37,]  175  154  227  184  157  144  123  185  164   161   156   167
> 162
> [38,]   71   73   70   84   93   91  105   77   92    78    77
> 62    81
> [39,]  802  498  744  807  888  692  617  798  743   720   720   778
> 881
> [40,]  274  213  311  310  320  258  250  321  278   283   291   199
> 254
>
> I've looked around in the annotation files from affymetrix and there
> are only 20 probes for this probeset.  Other probesets I've looked at
> have this issue too.  It seems that the number of probes groupt to
> that probeset are always doubled.  I am using the cdf which is located
> athttp://aroma-project.org/node/26, and the "Binary version of the
> CDF file (shown above) from Affymetrix.  54,675 units."
>
> Is this a mistake in the cdf file grouping of probes to probesets, or
> am I misunderstanding what the readUnits/readIntensities functions are
> doing?
>
> Fong

-- 
When reporting problems on aroma.affymetrix, make sure 1) to run the latest 
version of the package, 2) to report the output of sessionInfo() and 
traceback(), and 3) to post a complete code example.


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