ramfs or tmpfs without root ? Use /dev/shm
$ mkdir /dev/shm/mydata
$ ln -s /dev/shm/mydata ~/mydata
$ echo 'Some data' > ~/mydata/sample.txt
$ mkdir /dev/shm/mydata
$ ln -s /dev/shm/mydata ~/mydata
$ echo 'Some data' > ~/mydata/sample.txt