RNN package and problems with "Predictr"
The manual gives needed dimensions (see help on trainr function): 

Dimensions of input X need to be as: 

dim 1: samples
dim 2: time
dim 3: variables 


and dimensions of output Y should be: 

dim 1: samples (must be equal to dim 1 of X)
dim 2: time (must be equal to dim 2 of X)
dim 3: variables (could be 1 or more, if a matrix, will be coerce to array)