R help - Mar 2010 - Conditional replacement of NA depending on value in the previous column

Dear R-helpers,

I have a dataframe like this:

ID  X1  X2  X3  X4  X5  X6
49  1   1   1   0   NA  NA
50  1   1   1   1   NA  1

I would like to convert a missing value (NA) that follows a 0 (zero) or
another missing value (NA) into a 0 (zero).

So, the above lines would be converted to:

ID  X1  X2  X3  X4  X5  X6
49  1   1   1   0   0   0
50  1   1   1   1   NA  1

I have been struggling with this all morning, so any help you could provide
would be much appreciated.

Thank you!

Mark Na

	[[alternative HTML version deleted]]

Mark -
    Does this do what you want?

dat = data.frame(X1=c(1,1),X2=c(1,1),X3=c(1,1),
                  X4=c(0,1),X5=c(NA,NA),x6=c(NA,1))

fixit = function(x){
      y = c(x[-1],0)
      x[is.na(y) & is.na(x)] = 0
      x}

t(apply(dat,1,fixit))

      X1 X2 X3 X4 X5 x6
[1,]  1  1  1  0  0  0
[2,]  1  1  1  1 NA  1


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Tue, 23 Mar 2010, Mark Na wrote:
> Dear R-helpers,
>
> I have a dataframe like this:
>
> ID  X1  X2  X3  X4  X5  X6
> 49  1   1   1   0   NA  NA
> 50  1   1   1   1   NA  1
>
> I would like to convert a missing value (NA) that follows a 0 (zero) or
> another missing value (NA) into a 0 (zero).
>
> So, the above lines would be converted to:
>
> ID  X1  X2  X3  X4  X5  X6
> 49  1   1   1   0   0   0
> 50  1   1   1   1   NA  1
>
> I have been struggling with this all morning, so any help you could provide
> would be much appreciated.
>
> Thank you!
>
> Mark Na
>
> 	[[alternative HTML version deleted]]
>
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