util.array {CHNOSZ} | R Documentation |

## Functions to Work with Multidimensional Arrays

### Description

These functions can be used to turn a list into an array and extract or replace values or take the sum along a certain dimension of an array.

### Usage

```
list2array(l)
slice(arr, d = NULL, i = 1, value = NULL)
dimSums(arr, d = 1, i = NULL)
slice.affinity(affinity, d = 1, i = 1)
```

### Arguments

`l` |
a list. |

`arr` |
an array. |

`d` |
numeric, what dimension to use. |

`i` |
numeric, what slice to use. |

`value` |
values to assign to the portion of an array specified by |

`affinity` |
list, output from |

### Details

`list2array`

turns a list of `array`

s, each with the same dimensions, into a new array having one more dimension whose size is equal to the number of initial arrays.

`slice`

extracts or assigns values from/to the `i`

th slice(s) in the `d`

th dimension of an array. Values are assigned to an array if `value`

is not NULL. This function works by building an expression containing the extraction operator (`[`

).

`slice.affinity`

performs a slice operation on the ‘values’ element of the ‘affinity’ variable (which should be the output of `affinity`

).

`dimSums`

sums an array along the `d`

th dimension using only the `i`

th slices in that dimension. If `i`

is NULL, all slices in that dimension are summed together. For matrices, `dimSums(x,1)`

has the same result as `colSums(x)`

and `dimSums(x,2)`

has the same result as `rowSums(x)`

.

### Examples

```
# Start with a matrix
mat <- matrix(1:12, ncol = 3)
# Pay attention to the following when
# writing examples that test for identity!
identical(1 * mat, mat) # FALSE
# Create two matrices that are multiples of the first
a <- 1 * mat
b <- 2 * mat
# These both have two dimensions of lengths 4 and 3
dim(a) # 4 3
# Combine them to make an array with three dimensions
x <- list2array(list(a, b))
# The third dimension has length 2
dim(x) # 4 3 2
# The first slice of the third dimension
slice(x, 3) # a
# The second slice of the third dimension
slice(x, 3, 2) # b
# 'slice' works just like the bracket operator
slice(x, 1) # x[1, , ]
slice(x, 1, 2) # x[2, , ]
slice(x, 2, 1) # x[, 1, ]
slice(x, 2, 1:2) # x[, 1:2, ]
# Replace part of the array
y <- slice(x, 3, 2, value = a)
# Now the second slice of the third dimension == a
slice(y, 3, 2) # a
# and the sum across the third dimension == b
dimSums(y, 3) # b
# Taking the sum removes that dimension
dim(y) # 4 3 2
dim(dimSums(y, 1)) # 3 2
dim(dimSums(y, 2)) # 4 2
dim(dimSums(y, 3)) # 4 3
# Working with an 'affinity' object
basis("CHNOS+")
species("alanine")
a1 <- affinity(O2 = c(-80, -60)) # i.e. pH = 7
a2 <- affinity(O2 = c(-80, -60), pH = c(0, 14, 7))
# In the 2nd dimension (pH) get the 4th slice (pH = 7)
a3 <- slice.affinity(a2, 2, 4)
all.equal(a1$values, a3$values) # TRUE
```

*CHNOSZ*version 2.1.0 Index]