tensor.md
In ricci: Ricci Calculus

tensor diaginalization fails if dimensions do not agree

Code
  arr %_% .(i, i)
Condition
  Error in `arr %_% .(i, i)`:
  ! Attempted diagonal subsetting on slots with different dimensions.
  x Index `i` is associated to dimension 2 and 3.
  i Only assign identical index labels to slots with the equal dimension.

convert tensor to array works

Code
  as.array(arr %_% .(i, j), "i")
Condition
  Error:
  ! Argument `index_order` is not specified correctly.
  i Use `ricci::.()` to specify an index set.

convert tensor to array errs if index does not fit

Code
  as_a(arr %_% .(+i, j), j, i)
Condition
  Error in `as_a()`:
  ! Argument `...` contains index with incorrect position.
  x Position of index `-i` does not match index position in <Labeled Array> [2x2] .(+i, -j).
  i Make sure you explicitely specify the correct index position.

Code
  as_a(arr %_% .(+i, j), j)
Condition
  Error in `as_a()`:
  ! Argument `...` does not contain all indices.
  x Index `i` missing.
  i Operation requires the explicit selection of all indices.

creating a tensor errs when number index does not match

Code
  arr %_% .(i, j, k)
Condition
  Error in `arr %_% .(i, j, k)`:
  ! The number of provided indices do not match the array rank
  x 3 indices provided for a rank 2 array
  i The number of indices needs to match the array rank of argument `a`.