base::get function got object not found error ONLY under R CMD check R-package --as-cran

Question

The following code works perfectly well if called by source command. It is part of a function where xgb.metric.label is a formal parameter that at run time can be valorized with values like "rmsle" . bst.cv is a data.table .

 lab = paste('test.',xgb.metric.label,'.mean',sep='')
 bst.cv = xgboost::xgb.cv(param=param, data = data, label = y, 
                    nfold = nfold, nrounds=cv.nround , folds = foldList, 
                    feval = xgb.metric.fun , maximize = xgb.maximize, verbose=FALSE)

if (verbose) print(bst.cv)
early.stop = which(bst.cv[,get(lab)] == bst.cv[,min(get(lab))]  )

On the contrary when I call such a code by R CMD check R-package --as-cran I got the following error Error in get(lab) : object 'test.rmsle.mean' not found . But from the standard output I can see perfectly well test.rmsle.mean exists.

>> xgb: cross-validation ... 
      train.rmsle.mean train.rmsle.std test.rmsle.mean test.rmsle.std
   1:         1.982000        0.047535        1.971343       0.257277
   2:         1.957587        0.047260        1.947059       0.255464
   3:         1.933816        0.046985        1.923421       0.253643
   4:         1.910654        0.046711        1.900397       0.251813
   5:         1.888074        0.046436        1.877959       0.249975
  ---                                                                
2996:         0.267519        0.072264        0.307539       0.239068
2997:         0.267531        0.072254        0.307413       0.239195
2998:         0.267425        0.072160        0.307183       0.239163
2999:         0.267488        0.072168        0.307137       0.239798
3000:         0.267476        0.072201        0.307264       0.239906

I tried to call all the related libraries a line before the error, but without success.

library(data.table)
  library(xgboost)
  library(methods)

I also added these libraries in the imports section of DESCRIPTION file. Again, without success.

Imports:
    parallel, 
    subselect,
    plyr, 
    xgboost, 
    methods, 
    data.table 

Answer 1

Why are you using get at all?

There is no need to incur the overhead....

which(bst.cv[[lab]] == min(bst.cv[[lab]]))