R help - Apr 2003 - Code bug unresolved involving if condition

Hi R lovers!

I am a beginner in coding with R so my question may be very easily solved
but I don't know how.

I have written the following function in a .txt file


ClearDelta <- function(Matrix)
{
ncol<-ncol(Matrix);nrow<-nrow(Matrix);
for (i in 1:nrow) {
                  for (j in 1:(ncol-1))
                        {if (Matrix[i,j]==NA) (NA->Matrix[i,j+1])}
                  }
}

I can charge it with the source() command
But I get the following message when applied to a matrix
> ClearDelta(MatCor)
Error in if (Matrix[i, j] == NA) (Matrix[i, j + 1] <- NA) :
        missing value where logical needed

MatCor is the following Matrix
> MatCor
           [,1]         [,2]       [,3]
[1,]         NA          0.9870676  0.04648933
[2,] 0.98706757  1.0000000 -0.17353590
[3,] 0.04648933 -0.1735359  1.00000000

Do you know why I get such an unpleasant message from so polite a software?

Thanks to anybody who could help.







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The message is both pleasant and accurate!  It indicates that you have 
made an error, and tells you what the error is.

foo == NA is always missing, since NA denotes a missing value.
Use is.na(foo): see ?is.na.

On Fri, 25 Apr 2003 vincent.stoliaroff at socgen.com wrote:
> Hi R lovers!
> 
> I am a beginner in coding with R so my question may be very easily solved
> but I don't know how.
> 
> I have written the following function in a .txt file
> 
> 
> ClearDelta <- function(Matrix)
> {
> ncol<-ncol(Matrix);nrow<-nrow(Matrix);
> for (i in 1:nrow) {
>                   for (j in 1:(ncol-1))
>                         {if (Matrix[i,j]==NA) (NA->Matrix[i,j+1])}
>                   }
> }
> 
> I can charge it with the source() command
> But I get the following message when applied to a matrix
> 
> > ClearDelta(MatCor)
> Error in if (Matrix[i, j] == NA) (Matrix[i, j + 1] <- NA) :
>         missing value where logical needed
> 
> MatCor is the following Matrix
> 
> > MatCor
>            [,1]         [,2]       [,3]
> [1,]         NA          0.9870676  0.04648933
> [2,] 0.98706757  1.0000000 -0.17353590
> [3,] 0.04648933 -0.1735359  1.00000000
> 
> Do you know why I get such an unpleasant message from so polite a software?
> 
> Thanks to anybody who could help.
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

Thanks a lot
I had corrected that already after thinking for a while about the cause of
the bug

However I still have some trouble in trying to set the Matrix[i,j+1] term
to Missingness.

I am not sure how to use the generic function `is.na<-' which sets
elements
to `NA'.

      {if (is.na(Matrix[i,j])) (is.na(Matrix[i,j+1])<-1)}

does not work to set my  Matrix[i,j+1]  term to NA

Thanks in advance for any help




|---------+---------------------------->
|         |           ripley at stats.ox.a|
|         |           c.uk             |
|         |                            |
|         |           04/25/03 05:34 PM|
|         |                            |
|---------+---------------------------->
 
>------------------------------------------------------------------------------------------------------------------------------|
  |                                                                             
|
  |       To:       Vincent STOLIAROFF/fr/socgen at socgen                      
|
  |       cc:       r-help at stat.math.ethz.ch                                 
|
  |       Subject:  Re: [R] Code bug unresolved involving if condition          
|
 
>------------------------------------------------------------------------------------------------------------------------------|



The message is both pleasant and accurate!  It indicates that you have
made an error, and tells you what the error is.

foo == NA is always missing, since NA denotes a missing value.
Use is.na(foo): see ?is.na.

On Fri, 25 Apr 2003 vincent.stoliaroff at socgen.com wrote:
> Hi R lovers!
>
> I am a beginner in coding with R so my question may be very easily solved
> but I don't know how.
>
> I have written the following function in a .txt file
>
>
> ClearDelta <- function(Matrix)
> {
> ncol<-ncol(Matrix);nrow<-nrow(Matrix);
> for (i in 1:nrow) {
>                   for (j in 1:(ncol-1))
>                         {if (Matrix[i,j]==NA) (NA->Matrix[i,j+1])}
>                   }
> }
>
> I can charge it with the source() command
> But I get the following message when applied to a matrix
>
> > ClearDelta(MatCor)
> Error in if (Matrix[i, j] == NA) (Matrix[i, j + 1] <- NA) :
>         missing value where logical needed
>
> MatCor is the following Matrix
>
> > MatCor
>            [,1]         [,2]       [,3]
> [1,]         NA          0.9870676  0.04648933
> [2,] 0.98706757  1.0000000 -0.17353590
> [3,] 0.04648933 -0.1735359  1.00000000
>
> Do you know why I get such an unpleasant message from so polite a software?
>
> Thanks to anybody who could help.
--
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595







*************************************************************************
Ce message et toutes les pieces jointes (ci-apres le "message") sont
confidentiels et etablis a l'intention exclusive de ses destinataires.
Toute utilisation ou diffusion non autorisee est interdite. 
Tout message electronique est susceptible d'alteration. 
La SOCIETE GENERALE et ses filiales declinent toute responsabilite au 
titre de ce message s'il a ete altere, deforme ou falsifie.
				********
This message and any attachments (the "message") are confidentia...
{{dropped}}

On Fri, 25 Apr 2003 vincent.stoliaroff at socgen.com wrote:
> Hi R lovers!
>
> I am a beginner in coding with R so my question may be very easily solved
> but I don't know how.
>
> I have written the following function in a .txt file
>
>
> ClearDelta <- function(Matrix)
> {
> ncol<-ncol(Matrix);nrow<-nrow(Matrix);
> for (i in 1:nrow) {
>                   for (j in 1:(ncol-1))
>                         {if (Matrix[i,j]==NA) (NA->Matrix[i,j+1])}
>                   }
> }
>
> I can charge it with the source() command
> But I get the following message when applied to a matrix
>
> > ClearDelta(MatCor)
> Error in if (Matrix[i, j] == NA) (Matrix[i, j + 1] <- NA) :
>         missing value where logical needed
>
>
> Do you know why I get such an unpleasant message from so polite a software?
>
The test (Matrix[i,j] ==NA) returns NA, not TRUE or FALSE as you expected.
Think of NA as meaning "I don't know what this value is", so you
are
asking if Matrix[i,j] is equal to a number that you don't know. The answer
is that R doesn't know whether this is TRUE or FALSE, The value NA in a
logical variable means just that "This is TRUE or FALSE but I don't
know
which".  You can use is.na() test for NA, ie

  if(is.na(Matrix[i, j]))


I can't resist also pointing out that for large matrices there is a more
efficient answer

for(i in 1:nrow(Matrix))
	Matrix[i,]<- diff(c(0,cumsum(Matrix[i,])))


	-thomas