[R] Please help with loop, thanks

[Marc Schwartz]

Mark,

Sorry to come to the party late, but if the result vectors are going to be the same length:

mat <- matrix(rnorm(40), 10, 4)
colnames(mat) <- c("A","B","C","D")

> mat
               A            B           C           D
 [1,] -0.6489907 -1.000256771  0.69287228  0.81174708
 [2,]  0.1899992 -0.002432263  0.25729895 -1.75892514
 [3,] -0.8876303  0.918710108 -0.36694127  0.31080813
 [4,]  0.7344414 -1.619137824  0.46113302 -1.12355377
 [5,]  0.6041401 -1.214494484  0.09514796 -0.40251412
 [6,] -1.2832537  0.478327783 -0.27581631  0.38287704
 [7,] -0.2187174  0.656607367 -1.34435465 -0.03977851
 [8,]  0.7219878 -0.812492310 -0.37206013 -0.57919470
 [9,]  1.2644850  0.451997047  0.53445595  0.46368201
[10,]  0.2768631  0.756866311  1.27080049  0.74773388


If they are not:

individuals <- list(A = 5, B = 3, C = 7 , D = 10)

> lapply(individuals, rnorm)
$A
[1]  0.2985010 -1.6668673 -0.5972911 -0.4900159 -0.8235880

$B
[1]  0.3108316 -0.5031473 -0.7155617

$C
[1] -0.2670414  1.9196313 -2.0528845 -1.3008695 -0.6812742 -0.1673367
[7]  1.5839630

$D
 [1] -0.4027003 -0.4710862 -0.8342229  0.4622410  1.4038563  1.1073825
 [7] -0.2315623 -0.4758547  1.8888324 -0.4614643


HTH,

Marc Schwartz


On Mar 18, 2010, at 2:35 PM, Mark Na wrote:

> Many thanks to everyone who helped me solve this problem.
> 
> I think I must have described my problem poorly, but Phil, Patrick and Jim
> were able to see through the haze and suggest that I use a list to contain
> the output from my loop. This solution works very well.
> 
> Thanks again for your help, Mark
> 
> 
> 
> 
> On Thu, Mar 18, 2010 at 12:44 PM, Mark Na <mtb954 at gmail.com> wrote:
> 
>> Dear R helpers,
>> 
>> I would like to write a loop that makes 4 objects (called A, B, C, and D)
>> each of which contains ten random numbers.
>> 
>> This attempt:
>> 
>> individuals<-c("A","B","C","D")
>> for(i in 1:length(individuals)) {
>> individuals[i]<-rnorm(10)
>> }
>> 
>> 
>> does not work because "individuals[i]" is not the proper way to extract
>> each letter from the object called "individuals" (rather, it tries to assign
>> the random numbers to various positions within "individual")
>> 
>> So, my question is, what should be to the left of the gets operator in the
>> third line?
>> 
>> Many thanks,
>> 
>> Mark Na
>> 
> 
> 
> 
> -- 
> Mark Na
> University of Saskatchewan
> Saskatoon, Canada
> 
> 	[[alternative HTML version deleted]]
> 
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