[R] Loop or some other way to parse by data generated values when it is not linear

[Marc Schwartz]

On Mar 18, 2013, at 12:44 PM, plessthanpointohfive at gmail.com wrote:

> I'm sorry for the really vague subject line but I am not sure how to succinctly describe what I am doing and what the problem is.
> 
> But, here goes:
> 
> 1.  I have data with two-way data with frequencies.  Below is an example, though in reality I am looking at about 10 different variables that I am crossing so the values of X1 and X2 change.  X1 and X2 are place holders.
> 
> Here's the dataset (though using this first part does not happen in reality):
> 
> X1 <- matrix(c(0, 1, 2, 3, 4, 99), nrow=18, ncol=1, byrow=T)
> X2 <- sort(matrix(c(0, 2, 4), nrow=18, ncol=1, byrow=T), decreasing=F)
> Y <- matrix(c(83, 107, 47, 27, 38, 1, 12 ,25, 14, 4, 9, 0, 14, 27, 28, 13, 18, 0), nrow=18, ncol=1, byrow=T)
> tmp.n <- data.frame(X1, X2, Y)
> 
> The final data frame is what I actually get:
> 
> 
>   X1 X2   Y
> 1   0  0  83
> 2   1  0 107
> 3   2  0  47
> 4   3  0  27
> 5   4  0  38
> 6  99  0   1
> 7   0  2  12
> 8   1  2  25
> 9   2  2  14
> 10  3  2   4
> 11  4  2   9
> 12 99  2   0
> 13  0  4  14
> 14  1  4  27
> 15  2  4  28
> 16  3  4  13
> 17  4  4  18
> 18 99  4   0
> 
> 
> 2.  What I want is:
> 
> 
>         0   2   4
> 0     83 12 14
> 1   107 25 27
> 2     47 14 28
> 3     27   4 13
> 4     38   9 18
> 99     1   0   0
> 
> 
> 3.  I've been trying to do it using this (which is inside a function so I can vary what variables X1 and X2 are):
> 
> 
> X1 <- table(tmp.n[,1])
> X2 <- table(tmp.n[,2])
> 
> # Create the tmp.n.# datasets that contain the Y's.  Do this in a loop to automate
> dta <- NULL
> for (i in 0:length(X1)) {
> assign("tmp.n_", tmp.n[tmp.n[,1] == i, c(1,3)])
> tmp.n_ <- data.frame(tmp.n_[,2])
> dta[i] <- assign(paste("tmp.n.", i, sep=""), tmp.n_)
> dta
> }
> dta2 <- (data.frame(matrix(unlist(dta), nrow=n2[1], byrow=T)))
> colnames(dta2) <- names(X2)
> dta2
> 
> 
> And that works so long as X1 and X2 are linear.  In other words, if X1 <- seq(0, 4, 1).  But that 99 throws the whole thing off and it gives me this:
> 
>   X1 X2
> 1 107 25
> 2  27 47
> 3  14 28
> 4  27  4
> 5  13 38
> 6   9 18
> 
> It's basically breaks the whole thing.
> 
> I've not been able to figure this out and I've been like a dog with a bone trying to make it work with modifications to the for loop.  I know there is an easier way to do this, but my brain is no longer capable of thinking outside the box I've put it in.  So, I am turning to you for help.
> 
> Best,
> 
> Jen


Something like this?

> xtabs(Y ~ X1 + X2, data = tmp.n)
    X2
X1     0   2   4
  0   83  12  14
  1  107  25  27
  2   47  14  28
  3   27   4  13
  4   38   9  18
  99   1   0   0

See ?xtabs

Regards,

Marc Schwartz