Error while entering 'vim -c "helptags ~/.vim/doc" '

[paucazou]

Hello,
I'm very interested in your plugin. Unfortunately, the command written in the title return an error :
E150: ~/.vim/doc n'est pas un répertoire
.vim repertory exist. I tried to create the doc repertory and found the following error :
E151: Aucune correspondance : $USER/.vim/doc/**

Eventually, the plugin does not work. Have you got any clue to resolve this problem ?
Thanks in advance !