[R] Ops.factor(point1, point2) : - not meaningful for factors

[Rui Barradas]

Hello,

First of all, it's not a good idea to use  'dist' and 'diff' since they 
already are names of R functions.
As for the problem, your column DSi$Si is not a column of 2-dim points, 
it's not even a vector of numbers, it's a categorical variable,  a 
factor, like you can see in the output of str(). See the difference with 
an example, using your first two "points".


mydist <- function (point1, point2){
     dff <- point1 - point2
     distance <- sqrt(sum(dff^2))
     distance
}

x <- c(5, 20)  # these are vectors representing
y <- c(20, 2)  # 2-dim points

dist(matrix(c(x, y), ncol=2))
mydist(x, y)


Also, it's better to post data using ?dput().

Hope this helps,

Rui Barradas
Em 04-10-2012 09:07, nadiah escreveu:
> Hi, can anyone help me in this problem :(. I am a total beginner in R
> software.  It took me 2 days just to look into this problem.  Due to this
> problem. I cant do looping. i want to find the distance between x and DSi
>
>
>> DSi
>    i       Si
> 1 1  (5, 20)
> 2 2  (20, 2)
> 3 3 (25, 32)
> 4 4  (8, 39)
> 5 5 (10, 17)
> 6 6 (35, 20)
> 7 7 (38, 10)
>> str (DSi)
> 'data.frame':   7 obs. of  2 variables:
>   $ i : int  1 2 3 4 5 6 7
>   $ Si: Factor w/ 7 levels "(10, 17)","(20, 2)",..: 6 2 3 7 1 4 5
>> x <- c(15, 45)
>> y <- DSi [,2]
>> dist <- function (point1, point2)
> + {
> + diff <- point1-point2
> + distance <- sqrt(sum(diff^2))
> + distance
> + }
>> dist (x, y)
> [1] NA
> Warning message:
> In Ops.factor(point1, point2) : - not meaningful for factors
> Regards,
> Nadiah
>
>
>
> --
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