R: Converts vector indices to array indices

arrayIndex {R.utils} | R Documentation

## Converts vector indices to array indices

### Description

Converts vector indices to array indices assuming last array dimension to "move fastest", e.g. matrices are stored column by column.

### Usage

    ## Default S3 method:
    arrayIndex(i, dim, ...)

### Arguments

`i` | A `vector` of vector indices to be converted to array indices.
`dim` | A non-empty `numeric` `vector` specifying the dimension of the array.
`...` | Not used.

### Value

Returns an `integer` `matrix` of `length(i)` rows and `length(dim)` columns.

### References

[1] H. Bengtsson, Bayesian Networks - a self-contained introduction with implementation remarks, Master's Thesis in Computer Science, Mathematical Statistics, Lund Institute of Technology, 1999.

### See Also

From R v2.11.0 there is `arrayInd`(), which does the same thing as this method. `which`() with argument `arr.ind=TRUE`.

### Examples

    # Single index
    print(arrayIndex(21, dim=c(4,3,3)))

    # Multiple indices
    print(arrayIndex(20:23, dim=c(4,3,3)))

    # Whole array
    x <- array(1:30, dim=c(5,6))
    print(arrayIndex(1:length(x), dim=dim(x)))

    # Find (row,column) of maximum value
    m <- diag(4-abs(-4:4))
    print(arrayIndex(which.max(m), dim=dim(m)))

[Package R.utils version 2.7.0 Index]