diagram method does not check column names

[corybrunson]

diagram objects may be produced with deaths before births, in which case the Death column precedes the Birth column. This is not currently checked by as_persistence.diagram(), producing the buggy behavior below.

library(phutil)

# sublevel sets (conventional)
( d <- TDA::gridDiag(FUNvalues = volcano) )
#> $diagram
#>       dimension Birth Death
#>  [1,]         0    94   195
#>  [2,]         0   148   168
#>  [3,]         0   100   110
#>  [4,]         0   107   117
#>  [5,]         0   103   110
#>  [6,]         0    97   101
#>  [7,]         0   111   115
#>  [8,]         0   101   104
#>  [9,]         0   104   107
#> [10,]         0   105   107
#> [11,]         0   107   108
#> [12,]         0   100   101
#> [13,]         0    99   100
#> [14,]         1   124   195
#> [15,]         1   176   180
#> [16,]         1   166   170
#> [17,]         1   168   170
#> [18,]         1   107   108
#> [19,]         1   180   181
( p <- as_persistence(d) )
#> 
#> ── Persistence Data ────────────────────────────────────────────────────────────
#> ℹ There are 13 and 6 pairs in dimensions 0 and 1 respectively.
#> ℹ Computed from a Grid filtration using `TDA::gridDiag()`.
#> ℹ With the following parameters: FUNvalues = volcano.
p$pairs
#> [[1]]
#>       [,1] [,2]
#>  [1,]   94  195
#>  [2,]  148  168
#>  [3,]  100  110
#>  [4,]  107  117
#>  [5,]  103  110
#>  [6,]   97  101
#>  [7,]  111  115
#>  [8,]  101  104
#>  [9,]  104  107
#> [10,]  105  107
#> [11,]  107  108
#> [12,]  100  101
#> [13,]   99  100
#> 
#> [[2]]
#>      [,1] [,2]
#> [1,]  124  195
#> [2,]  176  180
#> [3,]  166  170
#> [4,]  168  170
#> [5,]  107  108
#> [6,]  180  181

# superlevel sets (unconventional)
( d <- TDA::gridDiag(FUNvalues = volcano, sublevel = FALSE) )
#> $diagram
#>      dimension Death Birth
#> [1,]         0    94   195
#> [2,]         0   166   170
#> [3,]         0   176   180
#> [4,]         0   168   170
#> [5,]         0   114   115
#> [6,]         0   107   108
#> [7,]         0   180   181
#> [8,]         1   148   168
( p <- as_persistence(d) )
#> 
#> ── Persistence Data ────────────────────────────────────────────────────────────
#> ℹ There are 7 and 1 pairs in dimensions 0 and 1 respectively.
#> ℹ Computed from a Grid filtration using `TDA::gridDiag()`.
#> ℹ With the following parameters: FUNvalues = volcano and sublevel = FALSE.
p$pairs
#> [[1]]
#>      [,1] [,2]
#> [1,]   94  195
#> [2,]  166  170
#> [3,]  176  180
#> [4,]  168  170
#> [5,]  114  115
#> [6,]  107  108
#> [7,]  180  181
#> 
#> [[2]]
#>      [,1] [,2]
#> [1,]  148  168

^{Created on 2025-10-26 with reprex v2.1.1}