[R] read dataset with blank space as missing value

[Yong Wang]

Dear R users

As specified in the subject, a dataset as following:

  56  a 1  2  3  4  5  6  7
234  b 2  3  5  .  8  1  9
457  b 2      4  6  7  3  3        <--the blank space should be missing value
658  f  2  3  5  6  8  1  9

the blank space at thethird row should be missing value. how should I
deal with this. fill=T will move "4" to the blank space which is not
desired.

thank you

yong