[R-sig-Geo] Dont show zero values in line graph

[Rainer M Krug]

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On 01/07/2011 08:43 AM, Edzer Pebesma wrote:
> 
> 
> On 01/07/2011 04:11 AM, jroll wrote:
>>
>> Hey everyone,
>>    Im getting better at plotting my data but cant for the life of me figure
>> out how to show a line graph with missing data that doesnt continue the line
>> down to zero then back up to the remaining values.
>>
>> Consider the following
>> x<-c(1:5,0,0,8:10)
>> y<-1:10
>>
>> plot(0,0,xlim=c(0,10), ylim=c(0,10),type="n",main="Dont show the bloody 0
>> values!!")
>> lines(x~y, col="blue", lwd=2,)
>>
>> My data is missing the 6th and 7th values and they come in as NA's so i
>> change them to 0s but then the plot has these ugly lines that dive toward
>> the x axis then back up.  I would do bar plots but i need to show multiple
>> sets of data on the same and side by side bars doesnt do it for me.  
>>
>> So i need a line graph that starts and stops where 0s or missing values
>> exist.  Thoughts?
> 
> x<-c(1:5,NA,NA,8:10)
> y<-1:10
> 
> plot(0,0,xlim=c(0,10), ylim=c(0,10),type="n",main="Dont show the bloody 0
> values!!")
> lines(x~y, col="blue", lwd=2,)

And just to complete it: to replace all the 0 in x with NA, you can do

x[x==0] <- NA

There is also the is.na() function which should do this, i.e.

is.na(x) <- 0

should (in my understanding) set all 0 values in x to NA - but it dose
not work, whereas setting e.g. all the 4s to NA works:

> x<-c(1:5,0,0,8:10)
> is.na(x) <- 0
> x
 [1]  1  2  3  4  5  0  0  8  9 10
> is.na(x) <- 4
> x
 [1]  1  2  3 NA  5  0  0  8  9 10
>

Why is this? Is this a bug in R or in y understanding?

Cheers,

Rainer
> 
>>
>> JR 
> 


- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

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