[R] if condition doesn't evaluate to True/False

[Bert Gunter]

test <- list(NULL)

Bert Gunter
Nonclinical Biostatistics
467-7374
 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Petr PIKAL
> Sent: Wednesday, April 29, 2009 8:21 AM
> To: ml-r-help at epigenomics.com
> Cc: r-help at stat.math.ethz.ch; Moumita Das
> Subject: Re: [R] if condition doesn't evaluate to True/False
> 
> Hi
> 
> r-help-bounces at r-project.org napsal dne 29.04.2009 17:05:01:
> 
> > see
> > ?is.null
> > 
> > e.g.
> > if( is.null(sub_grp_whr_cls_data[sbgrp_no, 1]) )
> > {
> >   your code
> > }
> 
> It probably will not work as 
> 
> sub_grp_whr_cls_data[sbgrp_no,1]=="NULL"
> 
> implicates that there is character value "NULL". I am not 
> sure if you can 
> get NULL as a part of some object. I tried and failed.
> See what you get
> x<- c(1,2,3, NULL)
> 
> Regards
> Petr
> 
> 
> > 
> > Moumita Das wrote:
> > > Hi friends,
> > > Please help me with this bug.
> > > 
> > > *Bug in my code:*
> > > 
> > > In this variable sub_grp_whr_cls_data[sbgrp_no,1] I store 
> the where
> > > clause.every sub group has a where condition linked with it.
> > > 
> > > Database1
> > > 
> > > 
> > > Where clause  was  not found for a particular subgroup,
> > > sub_grp_whr_cls_data[sbgrp_no,1]  value was NULL
> > > 
> > > So the condition (*sub_grp_whr_cls_data[sbgrp_no,1]=="NULL" ||
> > > sub_grp_whr_cls_data[sbgrp_no,1]==""*) should evaluate to 
> TRUE ,but it
> > > evaluated to NA
> > > 
> > > So the if block where I used the the condition threw error
> > > 
> > > If(*sub_grp_whr_cls_data[sbgrp_no,1]=="NULL" ||
> > > sub_grp_whr_cls_data[sbgrp_no,1]==""*)
> > > 
> > > i.e if(NA)
> > > 
> > > Error:--
> > > 
> > > Error in if (sub_grp_whr_cls_data[sbgrp_no, 1] == "NULL" ||
> > > sub_grp_whr_cls_data[sbgrp_no,  :
> > > 
> > >   missing value where TRUE/FALSE needed
> > > 
> > > Comments:-- but when there 's no where clause value the condition
> > > (sub_grp_whr_cls_data[sbgrp_no,1]=="NULL"
> > > ||sub_grp_whr_cls_data[sbgrp_no,1]=="") should 
> automatically evaluate 
> to *
> > > TRUE*
> > > 
> > > 
> > > 
> > > Database2
> > > 
> > > Where clause  was  found for a particular subgroup
> > > 
> > > The condition (sub_grp_whr_cls_data[sbgrp_no,1]=="NULL"
> > > ||sub_grp_whr_cls_data[sbgrp_no,1]=="") evaluated to FALSE
> > > 
> > > So if (sub_grp_whr_cls_data[sbgrp_no,1]=="NULL"
> > > ||sub_grp_whr_cls_data[sbgrp_no,1]=="") is
> > > 
> > > If (FALSE) ,control goes to the else part.
> > > 
> > > This is exactly what is expected of the program.
> > > 
> > > *QUERY:-- **If the condition evaluates to FALSE  when a where 
> condition is
> > > available why doesn't it evaluate to TRUE when a where condition 
> available
> > > is NULL or no where condition is available.*
> > > 
> > > Here I have taken the example of two databases where I 
> tried to get 
> the
> > > where clause for subgroup 1.In case of Database1 it was 
> not available 
> in
> > > case of Databse2 it was available.But the problem may 
> appear for the 
> same
> > > database also, when where clause is available for say one 
> subgroup and 
> not
> > > for the other.
> > > 
> > > 
> > > 
> > > 
> --------------------------------------------------------------
> ----------
> > > 
> > > ______________________________________________
> > > R-help at r-project.org mailing list
> > > 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.
> > 
> > 
> > -- 
> > Matthias Burger                     Project Manager/ Biostatistician
> > Epigenomics AG    Kleine Praesidentenstr. 1    10178 Berlin, Germany
> > phone:+49-30-24345-0                            fax:+49-30-24345-555
> > http://www.epigenomics.com           matthias.burger at epigenomics.com
> > --
> > Epigenomics AG Berlin           Amtsgericht Charlottenburg HRB 75861
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> >                                             Oliver Schacht PhD (CFO)
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> > 
> > ______________________________________________
> > R-help at r-project.org mailing list
> > 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.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>