[R] Matrix problems

[Adaikalavan Ramasamy]

  It 'unwraps' the 200,000 x 2 matrix into a vector with 400,000
elements and giving you the location/subscripts of this vector that
matches the criterion. Instead you should use  

apply(mat1, 2, function(y) which( y == 2 ))  

  which gives you the rows in each column that corresponds to 185.

Try length(mat1) and dim(mat1) and you will see that for length(), it
coerces the object into a vector first. 


-----Original Message-----
From: Mmarques INESC [mailto:mmarques at inescporto.pt] 
Sent: Thursday, March 20, 2003 7:49 PM
To: R-help Mailing list.
Subject: [R] Matrix problems


Hi all.
I do not know if it is a bug in the windows version but i have this
problem. Reading a file with 200000 rows, 2 columns and transforming
into a 200000 x 2 matrix. If I try to find an element by using the which
command which gives some correct indexes plus some others passing the
200000 row boundaries. If I try to reach those "outbound" indexs I get
an "Error: subscript out of bounds" . Is this a limitation of matrix
function ? or am i doing something wrong ? Example :

 > str(mat1)
 num [1:200000, 1:2] 185 212 222 269 342 349 361 367 397 423 ...  >
which(mat1 == 185)
  [1]      1 201920 203792 205211 206604 220417 223767 225169 239420
243768 249351 249395 252077
 What could be happening ?

 Thanks in advance
 Mark Marques

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