matrix_trace_test <- function ( )

#*****************************************************************************80
#
## matrix_trace_test() computes a matrix trace using einsum().
#
#  Licensing:
#
#    This code is distributed under the MIT license. 
#
#  Modified:
#
#    07 August 2026
#
#  Author:
#
#    John Burkardt
#
cat ( '\n' )
cat ( '  matrix_trace_test():\n' )

A = matrix ( c (
    11, 12, 13,
    21, 22, 23,
    31, 32, 33 ), nrow = 3, ncol = 3, byrow = TRUE )
cat ( '  A:\n' )
print ( A )

D = einsum ( 'ii ->', A )
cat ( '  D = einsum ( \'ii ->\', A ):\n' )
print ( D )