Hi,

If you read carefully the help pages for read.table you get this:


na.stringsa character vector of strings which are to be interpreted as
NA<../../utils/help/NA> values.
Blank fields are also considered to be missing values in logical, integer,
numeric and complex fields.

So, both NAs and blank fields are considered as NAs directly by read.table.

Once you have imported your data, you can modify with any of the string
manipulation functions (sub() or gsub()) to change your "#DIV/0!" to the
string "NAs". Another option is to manipulate your Excel file and consider
the division by cero with a "IF" and get back a NA if that happens.

And finally, instead of using na.omits use option na.rm=T to get done your
calculations:

> mean(c(12,23,24,45,67,NA), na.rm=T)[1] 34.2



Regards,
Carlos Ortega
www.qualityexcellence.es

On Thu, Sep 8, 2011 at 4:23 PM, Samir Benzerfa <benzerfa@gmx.ch> wrote:

> Hello everyone
>
>
>
> I have a couple of questions about the usage of the R function
> "read.table(.)". My point of departure is that I want to import a matrix
> (consisting of time and daily stock returns of many stocks) in R. Most of
> the data is numeric, however some values are missing (blanks) and in other
> cases I have the character "#DIV/0!" (from excel). My goal is to do some
> regression analysis with this matrix. My questions now are the following
> ones:
>
>
>
> 1.       How can I in general tell R to automatically replace some specific
> numbers or characters in tables by others? (for example to replace all
> characters "#DIV/0!" by the number 0 or simply "NA")
>
> 2.       How can I tell R to fill blanks with a number 0 or "NA"?
>
> 3.       How can I tell R to omit the "NA" fields in the calculations but
> not the whole row or column? (I realized that the function "na.omit" omits
> the whole row)
>
>
>
> Many thanks for your help!
>
>
>
> Sincerely,
>
> Samir
>
>
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>
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>

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