Hi all,



Assume  that I have a  data set (“xcv”) with several  variables  and some of
the variables have a missing observation  represented by -9 as shown below.
 I want to exclude these observations from the analysis ( as a NA).  Is
there a command that I can do it for the entire data set rather than one by
one for each variable ( tmp <- xcv[xcv$v1 != -9, ])



      V1 v2 v3 v4

11    23  14  -9

12    -9  21   3

     -9   30  41  25

     15   07 -9  10



 and I want the results as follows



      V1    v2     v3      v4

11       23    14     NA

       12   NA    21      3

       NA   30    41     25

        15     07   NA    10





The second question is I want to calculate the number of days between two
dates

    Start           end                 number of days

20020626    20020805             40

20030101    20030421             110



How do I do it in R?


Thanks in advance

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