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correlation between XY coordinates

5 messages · Christopher Kurby, Jeff Newmiller, Joshua Wiley +1 more

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Hello r world,

Does anyone know a function or package that can compute correlations between sets of XY coordinates?

Thanks in advance for your help,
Chris
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Isn't that one of the main things base R is used for?

Maybe your question is not specific enough. Can you provide some sample data and your best estimate of what the result should look like?
The Posting Guide mentioned below could help you elicit more effective answers.
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Christopher Kurby <kurbyc at gvsu.edu> wrote:

            
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Hi Chris,

As Jeff mentioned, it is hard to tell what you want (correlations
between sets of coordinates could mean many things it seems like to
me), but here is something that perhaps helps:

## some data (usually nice if you provide this rather than us having
to make something up)
d1 <- cbind(x <- rnorm(100), y <- rnorm(100))
d2 <- cbind(x2 = x + rnorm(100), y2 = y + rnorm(100))

## canonical correlation of the two matrices
cancor(d1, d2)

## simple correlation matrix of each dataset
cor(d1)
cor(d2)

Cheers,

Josh
On Sat, May 5, 2012 at 5:32 PM, Christopher Kurby <kurbyc at gvsu.edu> wrote:

  
    
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Hey Josh (and everyone),

My apologies, let me be more specific. I have two sets of XY coordinates in Cartesian space. I would like to compute a correlation between the two sets. For example, let's say I have two N X 2 matrices, with the first column being the X coordinate, the second column being the Y, and with each row being a new observation. I would like to know the strength the relationship between the two sets of coordinates (matrices). cancor provides two separate correlations, but I want a single value representing the strength of the relationship. Is this more clear?

Chris
On May 5, 2012, at 11:44 PM, Joshua Wiley wrote:

            
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Hi Chris,

To get a single value you might need something like a Mantel test, available in both ecodist and vegan. That test is a permutation test of significance of the correlation between two distance matrices.

Sarah
On May 6, 2012, at 8:06 AM, Christopher Kurby <kurbyc at gvsu.edu> wrote: