[R] Re : adding columns to a table after a loop

[Uwe Ligges]

Albert Picado wrote:
> Dear Uwe,
>  
> Thanks for your answer. I have been trying your suggestion but I haven't been able to solve my problem as I may have simplified in excess my example. The real situation is actually much similar to the following:
>  
> a<-1
> b<-1
> i<-1
> pvalue<-matrix()
> while(a<=4) {
>      while(b<=10){
>      pvalue[i]<-rnorm(1)
>      i<-i+1
>      b<-b+1
>      }
> a<-a+1
> }


I think you will have to read some basic documentation such as "An 
Introduction to R" about data structures, indexing, and loops in R 
before proceeding ...

Anyway, you can do:

a <- 1
pvalue <- matrix(nrow = 10, ncol = 4)
while(a <= 4) {
     b <- 1
     while(b <= 10){
         pvalue[b, a] <- rnorm(1)
         b <- b+1
     }
     a <- a+1
}


or much shorter


pvalue <- matrix(nrow = 10, ncol = 4)
for(a in 1:4) {
     for(b in 1:10){
         pvalue[b, a] <- rnorm(1)
     }
}


Uwe Ligges




> To get the desired outcome I have tried two things based on your suggestion:
>  
> 1)
>  
> a<-1
> b<-1
> i<-1
> pvalue<- matrix(ncol=4, nrow=10)
> result<- matrix()
> while(a<=4) {
>  while(b<=10){
>  pvalue[i]<-rnorm(1)
>  i<-i+1
>  b<-b+1
>  }
> result[,a]<-pvalue
> a<-a+1
> }
> 
> here I get an error message: 
> Error in "[<-"(`*tmp*`, , a, value = c(1.38661984066808, -0.641565430307799,  : 
>         number of items to replace is not a multiple of replacement length
> 
> 2)
>  
> a<-1
> b<-1
> i<-1
> pvalue<-matrix(ncol=4, nrow=10)
> while(a<=4) {
>  while(b<=10){
>  pvalue[i,a]<-rnorm(1)
>  i<-i+1
>  b<-b+1
>  }
> a<-a+1
> }
> 
> here what I get is:
>  
>> pvalue
>              [,1] [,2] [,3] [,4]
>  [1,] -2.18379100   NA   NA   NA
>  [2,] -0.90112392   NA   NA   NA
>  [3,] -0.91762163   NA   NA   NA
>  [4,]  0.54922398   NA   NA   NA
>  [5,]  0.95511590   NA   NA   NA
>  [6,]  0.08509518   NA   NA   NA
>  [7,] -0.92576835   NA   NA   NA
>  [8,]  1.62361191   NA   NA   NA
>  [9,]  0.02644486   NA   NA   NA
> [10,]  0.32406407   NA   NA   NA
> 
>  
> I do not know what else to try...
>  
> best wishes
>  
> a
> 
> 
> ----- Message d'origine ----
> De : Uwe Ligges <ligges at statistik.uni-dortmund.de>
> À : Albert Picado <albert_picado at yahoo.fr>
> Cc : r-help at stat.math.ethz.ch
> Envoyé le : Samedi, 12 Août 2006, 3h57mn 16s
> Objet : Re: [R] adding columns to a table after a loop
> 
> 
> Albert Picado wrote:
>> Dear list,
>>
>> I am trying to find the way to add columns to a table
>> (or a matrix) after a loop. The result of this loop is
>> an array and I would like to get all the results in a
>> single table once the loop is finish. I have
>> reproduced a simplified example below:
>>
>>> a<- 1
>>> b <- matrix()
>>> while (a <= 4) {
>> + b<-rnorm(10)
>> + a<- a +1
>> + }
> 
> 
> Staying in your example:
> 
> a <- 1
> b <- matrix(nrow=10, ncol=4)
> while(a <= 4){
>      b[,i] <- rnorm(10)
>      a <- a + 1
> }
> 
> Uwe Ligges
> 
> 
> 
>> # I have tried several methods but without succes so
>> far. 
>>
>>> result <- as.data.frame(cbind(b))
>>> result
>>              b
>> 1  -0.03250661
>> 2  -0.59823770
>> 3   1.58120471
>> 4   0.41086546
>> 5   0.78959090
>> 6   1.23587125
>> 7   0.83427190
>> 8   1.09035581
>> 9   0.11331056
>> 10  0.25267231
>>
>> the result above is not what I am looking for because
>> it shows only the results from the last operation in
>> the loop, I would like to obtain something like the
>> following.
>>
>>> result
>>             b1         b2          b3         b4
>> 1  -0.08420826 -0.0637943 -0.83246201 -1.0902384
>> 2   0.40623009 -2.7940096  1.37664973  1.6023967
>> 3  -1.13850505  1.1660669 -0.95962296 -0.7325098
>> 4  -1.06183391  1.1063677  1.67948677 -1.9875475
>> 5  -0.64431067 -0.4843952 -1.30742858  0.5064134
>> 6   0.56729468  1.0860484  0.07651954  0.4380108
>> 7   0.95036177 -0.5328609  1.28954934 -0.2775614
>> 8  -0.17848223  0.5340379 -0.22613700  1.0179886
>> 9   2.93145454 -1.8639607 -0.25478610  1.6619754
>> 10  1.51942415 -0.2051423  0.09144450 -1.6329481
>>
>> I hope someone can give me a hand
>>
>> best regards
>>
>> a
>>
>>
>>
>>
>>     
>>  p5.vert.ukl.yahoo.com uncompressed/chunked Sat Aug 12 13:14:00 GMT 2006
>>
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