[R] about data problem

[Jeff Newmiller]

Find the offending data. One approach is to look at the input data with your image sensors and neural pattern processor (eyes and brain). One way to reduce the load on those told is to read in the data with the stringsAsFactors=TRUE argument and try manually converting the resulting character strings into numeric values. You can then use the is.na function to find which rows failed to convert and use indexing to review the strings that had trouble. 

# I recommend against using df as a variable name, since it is the name of a function in base R
dta$DischargeNum <- as.numeric( dta$Discharge )
dta[ is.na( dta$DischargeNum ), "Discharge" ]
-- 
Sent from my phone. Please excuse my brevity.

On September 20, 2016 3:42:39 PM PDT, lily li <chocold12 at gmail.com> wrote:
>Thanks. Then what should I do to solve the problem?
>
>On Tue, Sep 20, 2016 at 4:30 PM, Jeff Newmiller
><jdnewmil at dcn.davis.ca.us>
>wrote:
>
>> I suppose you can do what works for your data, but I wouldn't
>recommend
>> na.rm=TRUE because it hides problems rather than clarifying them.
>>
>> If in fact your data includes true NA values (the letters NA or
>simply
>> nothing between the commas are typical ways this information may be
>> indicated), then read.csv will NOT change from integer to factor
>> (particularly if you have specified which markers represent NA using
>the
>> na.strings argument documented under read.table)... so you probably
>DO have
>> unexpected garbage still in your data which could be obscuring
>valuable
>> information that could affect your conclusions.
>> --
>> Sent from my phone. Please excuse my brevity.
>>
>> On September 20, 2016 3:11:42 PM PDT, lily li <chocold12 at gmail.com>
>wrote:
>> >I reread the data, and use 'na.rm = T' when reading the data. This
>time
>> >it
>> >has no such problem. It seems that the existence of NAs convert the
>> >integer
>> >to factor. Thanks for your help.
>> >
>> >
>> >On Tue, Sep 20, 2016 at 4:09 PM, Jianling Fan
><fanjianling at gmail.com>
>> >wrote:
>> >
>> >> Add the "stringsAsFactors = F"  when you read the data, and then
>> >> convert them to numeric.
>> >>
>> >> On 20 September 2016 at 16:00, lily li <chocold12 at gmail.com>
>wrote:
>> >> > Yes, it is stored as factor. I can't check out any problem in
>the
>> >> original
>> >> > data. Reread data doesn't help either. I use read.csv to read in
>> >the
>> >> data,
>> >> > do you think it is better to use read.table? Thanks again.
>> >> >
>> >> > On Tue, Sep 20, 2016 at 3:55 PM, Greg Snow <538280 at gmail.com>
>> >wrote:
>> >> >
>> >> >> This indicates that your Discharge column has been
>> >stored/converted as
>> >> >> a factor (run str(df) to verify and check other columns).  This
>> >> >> usually happens when functions like read.table are left to try
>to
>> >> >> figure out what each column is and it finds something in that
>> >column
>> >> >> that cannot be converted to a number (possibly an oh instead of
>a
>> >> >> zero, an el instead of a one, or just a letter or punctuation
>mark
>> >> >> accidentally in the file).  You can either find the error in
>your
>> >> >> original data, fix it, and reread the data, or specify that the
>> >column
>> >> >> should be numeric using the colClasses argument to read.table
>or
>> >other
>> >> >> function.
>> >> >>
>> >> >>
>> >> >>
>> >> >> On Tue, Sep 20, 2016 at 3:46 PM, lily li <chocold12 at gmail.com>
>> >wrote:
>> >> >> > Hi R users,
>> >> >> >
>> >> >> > I have a problem in reading data.
>> >> >> > For example, part of my dataframe is like this:
>> >> >> >
>> >> >> > df
>> >> >> > month day year          Discharge
>> >> >> >    3        1   2010                6.4
>> >> >> >    3        2   2010               7.58
>> >> >> >    3        3   2010               6.82
>> >> >> >    3        4   2010               8.63
>> >> >> >    3        5   2010               8.16
>> >> >> >    3        6   2010               7.58
>> >> >> >
>> >> >> > Then if I type summary(df), why it converts the discharge
>data
>> >to
>> >> >> levels? I
>> >> >> > also met the same problem when reading some other csv files.
>How
>> >to
>> >> solve
>> >> >> > this problem? Thanks.
>> >> >> >
>> >> >> > Discharge
>> >> >> > 7.58     :2
>> >> >> > 6.4       :1
>> >> >> > 6.82     :1
>> >> >> > 8.63     :1
>> >> >> > 8.16     :1
>> >> >> >
>> >> >> >         [[alternative HTML version deleted]]
>> >> >> >
>> >> >> > ______________________________________________
>> >> >> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
>> >see
>> >> >> > https://stat.ethz.ch/mailman/listinfo/r-help
>> >> >> > PLEASE do read the posting guide http://www.R-project.org/
>> >> >> posting-guide.html
>> >> >> > and provide commented, minimal, self-contained, reproducible
>> >code.
>> >> >>
>> >> >>
>> >> >>
>> >> >> --
>> >> >> Gregory (Greg) L. Snow Ph.D.
>> >> >> 538280 at gmail.com
>> >> >>
>> >> >
>> >> >         [[alternative HTML version deleted]]
>> >> >
>> >> > ______________________________________________
>> >> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
>see
>> >> > https://stat.ethz.ch/mailman/listinfo/r-help
>> >> > PLEASE do read the posting guide http://www.R-project.org/
>> >> posting-guide.html
>> >> > and provide commented, minimal, self-contained, reproducible
>code.
>> >>
>> >>
>> >>
>> >> --
>> >> Jianling Fan
>> >> 樊建凌
>> >>
>> >
>> >       [[alternative HTML version deleted]]
>> >
>> >______________________________________________
>> >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> >https://stat.ethz.ch/mailman/listinfo/r-help
>> >PLEASE do read the posting guide
>> >http://www.R-project.org/posting-guide.html
>> >and provide commented, minimal, self-contained, reproducible code.
>>
>>