R help - Mar 2005 - help for matrix formation.

Dear people, 

 I've been  trying to find a  way to do the following. 

I have a data set in text file with 3 columns and 2400 rows. i tried to read the
table as
fisrt<-("ex.txt",header=FALSE)
 
I would like to read the third column values (which has 2400 value) and split
them into matrix of size (600,4):
 
as 
first 600 column values in first column in matrix and next 600 next values(600
to 1200) as values in second column in matrix and so on.
 
and could you also suggest me how to retrieve those items in matrix like
matrix(520,3) =0 ...
 
thanks in advance for the help.
 

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


	[[alternative HTML version deleted]]

I'm not sure I am answereing your question, but here goes

# Create a vector with 2400 items
x <- runif(2400)

# Create a 600 by 4 matrix
y <- matrix(x,ncol = 4)

#If you needed the matrix to be done row by row
#y <- matrix(x,ncol = 4,byrow = T)

# Extract values from a particular part of the matrix
z <- y[500,3]  #row 500 column 3
z

# Extract values that meet certain criterion
z <- y[y < 0.01]
z

# Find postion of those that are extracted
which(y < 0.01)

HTH, Tom

> -----Original Message-----
> From: Lakshmi Dhevi Baskar [mailto:lavanya_ldb2000 at yahoo.co.in]
> Sent: Thursday, 17 March 2005 1:16 PM
> To: r-help-request at stat.math.ethz.ch
> Cc: r-help at stat.math.ethz.ch
> Subject: [R] help for matrix formation.
> 
> 
> Dear people, 
> 
>  I've been  trying to find a  way to do the following. 
> 
> I have a data set in text file with 3 columns and 2400 rows. 
> i tried to read the table as
> fisrt<-("ex.txt",header=FALSE)
>  
> I would like to read the third column values (which has 2400 
> value) and split them into matrix of size (600,4):
>  
> as 
> first 600 column values in first column in matrix and next 
> 600 next values(600 to 1200) as values in second column in 
> matrix and so on.
>  
> and could you also suggest me how to retrieve those items in 
> matrix like matrix(520,3) =0 ...
>  
> thanks in advance for the help.
>  
> 
> 		
> ---------------------------------
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
>