R: Miscellaneous vector functions

resolveVector {tractor.base} | R Documentation

## Miscellaneous vector functions

### Description

These functions provide the (Euclidean) length of a vector, the vector cross product or angle between two vectors.

### Usage

    resolveVector(len, ...)

    vectorLength(vector)

    vectorCrossProduct(a, b)

    angleBetweenVectors(v1, v2)

### Arguments

`len` | The expected length of the vector.
`...` | Elements of the vector, to be concatenated together.
`vector, v1, v2` | Numeric vectors of any length.
`a, b` | Numeric 3-vectors.

### Value

For `vectorLength`, the Euclidean norm or length of the specified vector, given by `sqrt(sum(vector^2))`. For `vectorCrossProduct`, the vector cross product of the two specified vectors; and for `angleBetweenVectors`, the angle (in radians) between the two specified vectors. The `resolveVector` function concatenates the values given in `...{}`, and if the result is a vector of length `len` then it is returned. If not, `NULL` is returned.

### Author(s)

Jon Clayden

### References

Please cite the following reference when using TractoR in your work:

J.D. Clayden, S. Muñoz Maniega, A.J. Storkey, M.D. King, M.E. Bastin & C.A. Clark (2011). TractoR: Magnetic resonance imaging and tractography with R. Journal of Statistical Software 44(8):1-18. http://www.jstatsoft.org/v44/i08/.

### See Also

`crossprod` for the matrix cross product.

[Package tractor.base version 3.2.2 Index]