Code bug unresolved involving if condition
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