R help - Sep 2007 - fail to recover decimal value from data frame

Hi,
I have some decimal values stored in a data frame (myframe) and I  
need to place them in a matrix (mymatrix) using a for loop.
When I type:

 > myframe[i,10]

I get:

[1] 0.8714
434 Levels: 0 0.0134 0.1062 0.1182 0.1241 0.1322 0.1374 0.1429  
0.1507 ... psi1

But when I assign that value to the matrix with:

 > mymatrix[i,2]<-myframe[i,10]

The value that gets placed in the matrix is 286, and not 0.8714 as I  
wanted it to be. What is wrong?
The data frame does have several rows of character cells interspersed  
with "NA" and decimal values. It is not very simple I am just using  
it to store a large output worksheet from where I want to draw  
selected values.

Thanks for any help.

G.

Hi,
> [1] 0.8714
> 434 Levels: 0 0.0134 0.1062 0.1182 0.1241 0.1322 0.1374 0.1429  
> 0.1507 ... psi1
The problem is that your data are not stored as numeric, but as a
factor.

You can see the following R FAQ entry to turn it back to a numeric
form :

http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-do-I-convert-factors-to-numeric_003f

HTH,

Julien

-- 
Julien Barnier
Groupe de recherche sur la socialisation
ENS-LSH - Lyon, France

Hi

you definitely shall try to get acustommed with data structures in R. You 
do ***not*** have numeric decimal values but factors (probably created by 
transfering data to R as you have in the column a value psi1).  Then the 
assignement places a factor code into matrix instead of a factor value. 

fac<-factor(rnorm(100))
daf<-as.data.frame(matrix(fac,10,10))
> sapply(daf, "is.factor")
  V1   V2   V3   V4   V5   V6   V7   V8   V9  V10 
TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE 

mat[1,10]<-daf[1,10]
> mat
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]   NA   NA   NA   NA   NA   NA   NA   NA   NA     1
 [2,]   NA   NA   NA   NA   NA   NA   NA   NA   NA    NA
 [3,]   NA   NA   NA   NA   NA   NA   NA   NA   NA    NA

<snip>
> mat[2,10]<-daf[2,10]
mat[2,10]
[1] 4
daf.n<-sapply(daf, function(x) as.numeric(as.character(x)))
mat[3,10]<-daf.n[3,10]
mat
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]     [,10]
 [1,]   NA   NA   NA   NA   NA   NA   NA   NA   NA 1.0000000
 [2,]   NA   NA   NA   NA   NA   NA   NA   NA   NA 4.0000000
 [3,]   NA   NA   NA   NA   NA   NA   NA   NA   NA 0.2200095
 [4,]   NA   NA   NA   NA   NA   NA   NA   NA   NA        NA
 [5,]   NA   NA   NA   NA   NA   NA   NA   NA   NA        NA
 
You need to get rid of irrelevant values in your data frame first.

Regards

Petr
petr.pikal at precheza.cz

r-help-bounces at r-project.org napsal dne 12.09.2007 16:03:36:
> Hi,
> I have some decimal values stored in a data frame (myframe) and I 
> need to place them in a matrix (mymatrix) using a for loop.
> When I type:
> 
>  > myframe[i,10]
> 
> I get:
> 
> [1] 0.8714
> 434 Levels: 0 0.0134 0.1062 0.1182 0.1241 0.1322 0.1374 0.1429 
> 0.1507 ... psi1
> 
> But when I assign that value to the matrix with:
> 
>  > mymatrix[i,2]<-myframe[i,10]
> 
> The value that gets placed in the matrix is 286, and not 0.8714 as I 
> wanted it to be. What is wrong?
> The data frame does have several rows of character cells interspersed 
> with "NA" and decimal values. It is not very simple I am just
using
> it to store a large output worksheet from where I want to draw 
> selected values.
> 
> Thanks for any help.
> 
> G.
> 
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